vim-patch:9.1.0982: TI linker files are not recognized

Problem:  TI linker files are not recognized
Solution: inspect '*.cmd' files and detect TI linker files
          as 'lnk' filetype, include a lnk ftplugin and syntax
          script (Wu, Zhenyu)

closes: vim/vim#16320

39a4eb0b2c

Co-authored-by: Wu, Zhenyu <wuzhenyu@ustc.edu>

test/old/testdir/test_filetype.vim

@@ -2300,6 +2300,27 @@ func Test_cls_file()
   filetype off
 endfunc
 
+func Test_cmd_file()
+  filetype on
+
+  call writefile(['--rom_model'], 'Xfile.cmd')
+  split Xfile.cmd
+  call assert_equal('lnk', &filetype)
+  bwipe!
+
+  call writefile(['/* comment */'], 'Xfile.cmd')
+  split Xfile.cmd
+  call assert_equal('rexx', &filetype)
+  bwipe!
+
+  call writefile(['REM comment'], 'Xfile.cmd')
+  split Xfile.cmd
+  call assert_equal('dosbatch', &filetype)
+  bwipe!
+
+  filetype off
+endfunc
+
 func Test_sig_file()
   filetype on