patch 9.0.0006: not all Visual Basic files are recognized

Problem:    Not all Visual Basic files are recognized.
Solution:   Change detection of *.cls files. (Doug Kearns)
diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 01cde46..5f48f4b 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -72,22 +72,35 @@
 
   # most frequent FreeBASIC-specific keywords in distro files
   var fb_keywords = '\c^\s*\%(extern\|var\|enum\|private\|scope\|union\|byref\|operator\|constructor\|delete\|namespace\|public\|property\|with\|destructor\|using\)\>\%(\s*[:=(]\)\@!'
-  var fb_preproc  = '\c^\s*\%(#\a\+\|option\s\+\%(byval\|dynamic\|escape\|\%(no\)\=gosub\|nokeyword\|private\|static\)\>\)'
+  var fb_preproc  = '\c^\s*\%(' ..
+                      # preprocessor
+                      '#\s*\a\+\|' ..
+                      # compiler option
+                      'option\s\+\%(byval\|dynamic\|escape\|\%(no\)\=gosub\|nokeyword\|private\|static\)\>\|' ..
+                      # metacommand
+                      '\%(''\|rem\)\s*\$lang\>\|' ..
+                      # default datatype
+                      'def\%(byte\|longint\|short\|ubyte\|uint\|ulongint\|ushort\)\>' ..
+                    '\)'
   var fb_comment  = "^\\s*/'"
+
   # OPTION EXPLICIT, without the leading underscore, is common to many dialects
   var qb64_preproc = '\c^\s*\%($\a\+\|option\s\+\%(_explicit\|_\=explicitarray\)\>\)'
 
-  var lines = getline(1, min([line("$"), 100]))
-
-  if match(lines, fb_preproc) > -1 || match(lines, fb_comment) > -1 || match(lines, fb_keywords) > -1
-    setf freebasic
-  elseif match(lines, qb64_preproc) > -1
-    setf qb64
-  elseif match(lines, ft_visual_basic_content) > -1
-    setf vb
-  else
-    setf basic
-  endif
+  for lnum in range(1, min([line("$"), 100]))
+    var line = getline(lnum)
+    if line =~ ft_visual_basic_content
+      setf vb
+      return
+    elseif line =~ fb_preproc || line =~ fb_comment || line =~ fb_keywords
+      setf freebasic
+      return
+    elseif line =~ qb64_preproc
+      setf qb64
+      return
+    endif
+  endfor
+  setf basic
 enddef
 
 export def FTbtm()
@@ -126,6 +139,23 @@
   endif
 enddef
 
+export def FTcls()
+  if exists("g:filetype_cls")
+    exe "setf " .. g:filetype_cls
+    return
+  endif
+
+  if getline(1) =~ '^%'
+    setf tex
+  elseif getline(1)[0] == '#' && getline(1) =~ 'rexx'
+    setf rexx
+  elseif getline(1) == 'VERSION 1.0 CLASS'
+    setf vb
+  else
+    setf st
+  endif
+enddef
+
 export def FTlpc()
   if exists("g:lpc_syntax_for_c")
     var lnum = 1
diff --git a/runtime/doc/filetype.txt b/runtime/doc/filetype.txt
index 06eff2d..282a796 100644
--- a/runtime/doc/filetype.txt
+++ b/runtime/doc/filetype.txt
@@ -143,6 +143,7 @@
 	*.asp		g:filetype_asp	|ft-aspvbs-syntax| |ft-aspperl-syntax|
 	*.bas		g:filetype_bas	|ft-basic-syntax|
 	*.cfg		g:filetype_cfg
+	*.cls		g:filetype_cls
 	*.csh		g:filetype_csh	|ft-csh-syntax|
 	*.dat		g:filetype_dat
 	*.frm		g:filetype_frm	|ft-form-syntax|
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index 6280d32..1648e82 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -1798,16 +1798,11 @@
 au BufNewFile,BufRead .slrnrc			setf slrnrc
 au BufNewFile,BufRead *.score			setf slrnsc
 
-" Smalltalk (and TeX)
+" Smalltalk
 au BufNewFile,BufRead *.st			setf st
-au BufNewFile,BufRead *.cls
-	\ if getline(1) =~ '^%' |
-	\  setf tex |
-	\ elseif getline(1)[0] == '#' && getline(1) =~ 'rexx' |
-	\  setf rexx |
-	\ else |
-	\  setf st |
-	\ endif
+
+" Smalltalk (and Rexx, TeX, and Visual Basic)
+au BufNewFile,BufRead *.cls                     call dist#ft#FTcls()
 
 " Smarty templates
 au BufNewFile,BufRead *.tpl			setf smarty