patch 8.2.4747: no filetype override for .sys files

Problem:    No filetype override for .sys files.
Solution:   Add g:filetype_sys. (Patrick Meiser-Knosowski, closes #10181)
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 34868d6..a94002e 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -1501,7 +1501,7 @@
 func Test_sc_file()
   filetype on
 
-  " SC file mehtods are defined 'Class : Method'
+  " SC file methods are defined 'Class : Method'
   call writefile(['SCNvimDocRenderer : SCDocHTMLRenderer {'], 'srcfile.sc')
   split srcfile.sc
   call assert_equal('supercollider', &filetype)
@@ -1588,6 +1588,13 @@
   call assert_equal('bat', &filetype)
   bwipe!
 
+  " Users preference set by g:filetype_sys
+  let g:filetype_sys = 'sys'
+  split sysfile.sys
+  call assert_equal('sys', &filetype)
+  unlet g:filetype_sys
+  bwipe!
+
   " RAPID header start with a line containing only "%%%", 
   " but is not always present.
   call writefile(['%%%'], 'sysfile.sys')
diff --git a/src/version.c b/src/version.c
index e3ba0c8..9f99177 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4747,
+/**/
     4746,
 /**/
     4745,