patch 9.0.1182: go checksum files are not recognized

Problem:    go checksum files are not recognized.
Solution:   Add the name of go checksum files. (Amaan Qureshi, closes #11803)

runtime/filetype.vim

@@ -849,6 +849,9 @@ au BufNewFile,BufRead *.htpp			setf hastepreproc
 " HCL
 au BufRead,BufNewFile *.hcl			setf hcl
 
+" Go checksum file (must be before *.sum Hercules)
+au BufNewFile,BufRead go.sum			setf gosum
+
 " Hercules
 au BufNewFile,BufRead *.vc,*.ev,*.sum,*.errsum	setf hercules
 

src/testdir/test_filetype.vim

@@ -230,6 +230,7 @@ let s:filename_checks = {
     \ 'gnuplot': ['file.gpi', '.gnuplot'],
     \ 'go': ['file.go'],
     \ 'gomod': ['go.mod'],
+    \ 'gosum': ['go.sum'],
     \ 'gowork': ['go.work'],
     \ 'gp': ['file.gp', '.gprc'],
     \ 'gpg': ['/.gnupg/options', '/.gnupg/gpg.conf', '/usr/any/gnupg/options.skel', 'any/.gnupg/gpg.conf', 'any/.gnupg/options', 'any/usr/any/gnupg/options.skel'],

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1182,
 /**/
     1181,
 /**/