patch 8.2.0003: Build file dependencies are incomplete

Problem:    Build file dependencies are incomplete.
Solution:   Fix the dependencies. (Ken Takata, closes #5356)
diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index dc5ef8d..3bf552a 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -107,6 +107,25 @@
   endif
 enddef
 
+# Returns true if file content looks like RAPID
+def IsRapid(sChkExt: string = ""): bool
+  if sChkExt == "cfg"
+    return getline(1) =~? '\v^%(EIO|MMC|MOC|PROC|SIO|SYS):CFG'
+  endif
+  # called from FTmod, FTprg or FTsys
+  return getline(nextnonblank(1)) =~? '\v^\s*%(\%{3}|module\s+\k+\s*%(\(|$))'
+enddef
+
+export def FTcfg()
+  if exists("g:filetype_cfg")
+    exe "setf " .. g:filetype_cfg
+  elseif IsRapid("cfg")
+    setf rapid
+  else
+    setf cfg
+  endif
+enddef
+
 export def FTlpc()
   if exists("g:lpc_syntax_for_c")
     var lnum = 1
@@ -168,7 +187,7 @@
 
 export def FTent()
   # This function checks for valid cl syntax in the first five lines.
-  # Look for either an opening comment, '#', or a block start, '{".
+  # Look for either an opening comment, '#', or a block start, '{'.
   # If not found, assume SGML.
   var lnum = 1
   while lnum < 6
@@ -410,6 +429,36 @@
   setf nroff
 enddef
 
+# Returns true if file content looks like LambdaProlog
+def IsLProlog(): bool
+  # skip apparent comments and blank lines, what looks like 
+  # LambdaProlog comment may be RAPID header
+  var l: number = nextnonblank(1)
+  while l > 0 && l < line('$') && getline(l) =~ '^\s*%' # LambdaProlog comment
+    l = nextnonblank(l + 1)
+  endwhile
+  # this pattern must not catch a go.mod file
+  return getline(l) =~ '\<module\s\+\w\+\s*\.\s*\(%\|$\)'
+enddef
+
+# Determine if *.mod is ABB RAPID, LambdaProlog, Modula-2, Modsim III or go.mod
+export def FTmod()
+  if exists("g:filetype_mod")
+    exe "setf " .. g:filetype_mod
+  elseif IsLProlog()
+    setf lprolog
+  elseif getline(nextnonblank(1)) =~ '\%(\<MODULE\s\+\w\+\s*;\|^\s*(\*\)'
+    setf modula2
+  elseif IsRapid()
+    setf rapid
+  elseif expand("<afile>") =~ '\<go.mod$'
+    setf gomod
+  else
+    # Nothing recognized, assume modsim3
+    setf modsim3
+  endif
+enddef
+
 export def FTpl()
   if exists("g:filetype_pl")
     exe "setf " .. g:filetype_pl
@@ -526,6 +575,18 @@
   endif
 enddef
 
+# Determine if *.prg is ABB RAPID. Can also be Clipper, FoxPro or eviews
+export def FTprg()
+  if exists("g:filetype_prg")
+    exe "setf " .. g:filetype_prg
+  elseif IsRapid()
+    setf rapid
+  else
+    # Nothing recognized, assume Clipper
+    setf clipper
+  endif
+enddef
+
 export def FTr()
   var max = line("$") > 50 ? 50 : line("$")
 
@@ -572,7 +633,7 @@
       return
     endif
   endfor
-  setf m4  " Default: Sendmail .mc file
+  setf m4  # Default: Sendmail .mc file
 enddef
 
 # Called from filetype.vim and scripts.vim.
@@ -735,6 +796,14 @@
   return 0
 enddef
 
+export def FTsys()
+  if IsRapid()
+    setf rapid
+  else
+    setf bat
+  endif
+enddef
+
 # Choose context, plaintex, or tex (LaTeX) based on these rules:
 # 1. Check the first line of the file for "%&<format>".
 # 2. Check the first 1000 non-comment lines for LaTeX or ConTeXt keywords.
diff --git a/runtime/doc/filetype.txt b/runtime/doc/filetype.txt
index aa8e995..0274a73 100644
--- a/runtime/doc/filetype.txt
+++ b/runtime/doc/filetype.txt
@@ -148,6 +148,7 @@
 	*.i		g:filetype_i	|ft-progress-syntax|
 	*.inc		g:filetype_inc
 	*.m		g:filetype_m	|ft-mathematica-syntax|
+	*.mod		g:filetype_mod
 	*.p		g:filetype_p	|ft-pascal-syntax|
 	*.pl		g:filetype_pl
 	*.pp		g:filetype_pp	|ft-pascal-syntax|
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index 0c7dcae..2e87abc 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -205,11 +205,13 @@
 " FreeBasic file (similar to QBasic)
 au BufNewFile,BufRead *.fb			setf freebasic
 
-" Batch file for MSDOS.
-au BufNewFile,BufRead *.bat,*.sys		setf dosbatch
+" Batch file for MSDOS. See dist#ft#FTsys for *.sys
+au BufNewFile,BufRead *.bat 			setf dosbatch
 " *.cmd is close to a Batch file, but on OS/2 Rexx files also use *.cmd.
 au BufNewFile,BufRead *.cmd
 	\ if getline(1) =~ '^/\*' | setf rexx | else | setf dosbatch | endif
+" ABB RAPID or Batch file for MSDOS.
+au BufNewFile,BufRead *.sys\c 			call dist#ft#FTsys()
 
 " Batch file for 4DOS
 au BufNewFile,BufRead *.btm			call dist#ft#FTbtm()
@@ -360,13 +362,8 @@
 " Clever or dtd
 au BufNewFile,BufRead *.ent			call dist#ft#FTent()
 
-" Clipper (or FoxPro; could also be eviews)
-au BufNewFile,BufRead *.prg
-	\ if exists("g:filetype_prg") |
-	\   exe "setf " . g:filetype_prg |
-	\ else |
-	\   setf clipper |
-	\ endif
+" Clipper, FoxPro, ABB RAPID or eviews
+au BufNewFile,BufRead *.prg\c			call dist#ft#FTprg()
 
 " Clojure
 au BufNewFile,BufRead *.clj,*.cljs,*.cljx,*.cljc		setf clojure
@@ -444,7 +441,7 @@
 au BufNewFile,BufRead *.qc			setf c
 
 " Configure files
-au BufNewFile,BufRead *.cfg			setf cfg
+au BufNewFile,BufRead *.cfg\c			call dist#ft#FTcfg()
 
 " Cucumber
 au BufNewFile,BufRead *.feature			setf cucumber
@@ -980,7 +977,7 @@
 " Limits
 au BufNewFile,BufRead */etc/limits,*/etc/*limits.conf,*/etc/*limits.d/*.conf	setf limits
 
-" LambdaProlog (*.mod too, see Modsim)
+" LambdaProlog (see dist#ft#FTmod for *.mod)
 au BufNewFile,BufRead *.sig			setf lprolog
 
 " LDAP LDIF
@@ -1143,18 +1140,11 @@
 " Symbian meta-makefile definition (MMP)
 au BufNewFile,BufRead *.mmp			setf mmp
 
-" Modsim III (or LambdaProlog)
-au BufNewFile,BufRead *.mod
-	\ if expand("<afile>") =~ '\<go.mod$' |
-	\   setf gomod |
-	\ elseif getline(1) =~ '\<module\>' |
-	\   setf lprolog |
-	\ else |
-	\   setf modsim3 |
-	\ endif
+" ABB Rapid, Modula-2, Modsim III or LambdaProlog
+au BufNewFile,BufRead *.mod\c 			call dist#ft#FTmod()
 
-" Modula-2  (.md removed in favor of Markdown)
-au BufNewFile,BufRead *.m2,*.DEF,*.MOD,*.mi	setf modula2
+" Modula-2  (.md removed in favor of Markdown, see dist#ft#FTmod for *.MOD)
+au BufNewFile,BufRead *.m2,*.DEF,*.mi		setf modula2
 
 " Modula-3 (.m3, .i3, .mg, .ig)
 au BufNewFile,BufRead *.[mi][3g]		setf modula3