patch 9.1.0013: Modula2 filetype support lacking

Problem:  Modula2 filetype support lacking
Solution: Improve the Modula-2 runtime support, add additional modula2
          dialects, add compiler plugin, update syntax highlighting,
          include syntax tests, update Makefiles (Doug Kearns)

closes: #6796
closes: #8115

Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Benjamin Kowarsch <trijezdci@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/compiler/gm2.vim

@@ -0,0 +1,26 @@
+" Vim compiler file
+" Compiler:	GNU Modula-2 Compiler
+" Maintainer:	Doug Kearns <dougkearns@gmail.com>
+" Last Change:	2024 Jan 04
+
+if exists("current_compiler")
+  finish
+endif
+let current_compiler = "gm2"
+
+if exists(":CompilerSet") != 2		" older Vim always used :setlocal
+  command -nargs=* CompilerSet setlocal <args>
+endif
+
+let s:cpo_save = &cpo
+set cpo&vim
+
+CompilerSet makeprg=gm2
+CompilerSet errorformat=%-G%f:%l:%c:\ error:\ compilation\ failed,
+		       \%f:%l:%c:\ %trror:\ %m,
+		       \%f:%l:%c:\ %tarning:\ %m,
+		       \%f:%l:%c:\ %tote:\ %m,
+		       \%-G%.%#
+
+let &cpo = s:cpo_save
+unlet s:cpo_save