patch 8.2.1458: .gawk files not recognized

Problem:    .gawk files not recognized.
Solution:   Recognize .gawk files. (Doug Kearns)

runtime/filetype.vim

@@ -184,7 +184,7 @@ au BufNewFile,BufRead *.at			setf m4
 au BufNewFile,BufRead *.ave			setf ave
 
 " Awk
-au BufNewFile,BufRead *.awk			setf awk
+au BufNewFile,BufRead *.awk,*.gawk		setf awk
 
 " B
 au BufNewFile,BufRead *.mch,*.ref,*.imp		setf b

src/testdir/test_filetype.vim

@@ -73,7 +73,7 @@ let s:filename_checks = {
     \ 'autoit': ['file.au3'],
     \ 'automake': ['GNUmakefile.am'],
     \ 'ave': ['file.ave'],
-    \ 'awk': ['file.awk'],
+    \ 'awk': ['file.awk', 'file.gawk'],
     \ 'b': ['file.mch', 'file.ref', 'file.imp'],
     \ 'bc': ['file.bc'],
     \ 'bdf': ['file.bdf'],
@@ -597,7 +597,8 @@ let s:script_checks = {
       \ 'bc': [['#!/path/bc']],
       \ 'sed': [['#!/path/sed']],
       \ 'ocaml': [['#!/path/ocaml']],
-      \ 'awk': [['#!/path/awk']],
+      \ 'awk': [['#!/path/awk'],
+      \         ['#!/path/gawk']],
       \ 'wml': [['#!/path/wml']],
       \ 'scheme': [['#!/path/scheme']],
       \ 'cfengine': [['#!/path/cfengine']],

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1458,
 /**/
     1457,
 /**/