patch 9.0.2128: runtime(swig): add syntax and filetype plugins

Add syntax and filetype plugins for SWIG (Simplified Wrapper Interface
Generator) description files.

The default syntax for .i files highlights comments in a reverse
color scheme which doesn't look well.  This syntax builds
on vim's c++ syntax by adding highlighting for common swig
directives and user defined directives.  For an alternative
syntax, see vimscript #1247 (which I found after writing this).

closes: #13562

Co-authored-by: Matěj Cepl <mcepl@cepl.eu>
Co-authored-by: Julien Marrec <julien.marrec@gmail.com>
Signed-off-by: Julien Marrec <julien.marrec@gmail.com>
Signed-off-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_filetype.vim

@@ -673,6 +673,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     swayconfig: ['/home/user/.sway/config', '/home/user/.config/sway/config', '/etc/sway/config', '/etc/xdg/sway/config'],
     swift: ['file.swift'],
     swiftgyb: ['file.swift.gyb'],
+    swig: ['file.swg', 'file.swig'],
     sysctl: ['/etc/sysctl.conf', '/etc/sysctl.d/file.conf', 'any/etc/sysctl.conf', 'any/etc/sysctl.d/file.conf'],
     systemd: ['any/systemd/file.automount', 'any/systemd/file.dnssd',
               'any/systemd/file.link', 'any/systemd/file.mount',
@@ -2340,4 +2341,34 @@ func Test_vba_file()
   filetype off
 endfunc
 
+func Test_i_file()
+  filetype on
+
+  " Swig: keyword
+  call writefile(['%module mymodule', '/* a comment */'], 'Xfile.i', 'D')
+  split Xfile.i
+  call assert_equal('swig', &filetype)
+  bwipe!
+
+  " Swig: verbatim block
+  call writefile(['%{', '#include <header.hpp>', '%}'], 'Xfile.i', 'D')
+  split Xfile.i
+  call assert_equal('swig', &filetype)
+  bwipe!
+
+  " ASM
+  call writefile(['; comment', ';'], 'Xfile.i', 'D')
+  split Xfile.i
+  call assert_equal('asm', &filetype)
+  bwipe!
+
+  " *.i defaults to progress
+  call writefile(['looks like progress'], 'Xfile.i', 'D')
+  split Xfile.i
+  call assert_equal('progress', &filetype)
+  bwipe!
+
+  filetype off
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2128,
 /**/
     2127,
 /**/