patch 9.0.1407: TableGen files are not recognized

Problem:    TableGen files are not recognized.
Solution:   Add a pattern for TableGen files. (Amaan Qureshi, closes #12156)

runtime/filetype.vim

@@ -2105,6 +2105,9 @@ au BufNewFile,BufRead *.svg			setf svg
 " Surface
 au BufRead,BufNewFile *.sface			setf surface
 
+" LLVM TableGen
+au BufNewFile,BufRead *.td			setf tablegen
+
 " Tads (or Nroff or Perl test file)
 au BufNewFile,BufRead *.t
 	\ if !dist#ft#FTnroff() && !dist#ft#FTperl() | setf tads | endif

src/testdir/test_filetype.vim

@@ -587,6 +587,7 @@ let s:filename_checks = {
     \ 'taskdata': ['pending.data', 'completed.data', 'undo.data'],
     \ 'taskedit': ['file.task'],
     \ 'tcl': ['file.tcl', 'file.tm', 'file.tk', 'file.itcl', 'file.itk', 'file.jacl', '.tclshrc', 'tclsh.rc', '.wishrc'],
+    \ 'tablegen': ['file.td'],
     \ 'teal': ['file.tl'],
     \ 'template': ['file.tmpl'],
     \ 'teraterm': ['file.ttl'],

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1407,
 /**/
     1406,
 /**/