patch 8.2.4251: vala files are not recognized

Problem:    Vala files are not recognized.
Solution:   Add the *.vala pattern. (closes #9654)

runtime/filetype.vim

@@ -2018,6 +2018,9 @@ au BufNewFile,BufRead */.init/*.conf,*/.init/*.override	       setf upstart
 au BufNewFile,BufRead */.config/upstart/*.conf		       setf upstart
 au BufNewFile,BufRead */.config/upstart/*.override	       setf upstart
 
+" Vala
+au BufNewFile,BufRead *.vala			setf vala
+
 " Vera
 au BufNewFile,BufRead *.vr,*.vri,*.vrh		setf vera
 

src/testdir/test_filetype.vim

@@ -557,6 +557,7 @@ let s:filename_checks = {
     \ 'usserverlog': ['usserver.log', 'USSERVER.LOG', 'usserver.file.log', 'USSERVER.FILE.LOG', 'file.usserver.log', 'FILE.USSERVER.LOG'],
     \ 'usw2kagtlog': ['usw2kagt.log', 'USW2KAGT.LOG', 'usw2kagt.file.log', 'USW2KAGT.FILE.LOG', 'file.usw2kagt.log', 'FILE.USW2KAGT.LOG'],
     \ 'vb': ['file.sba', 'file.vb', 'file.vbs', 'file.dsm', 'file.ctl'],
+    \ 'vala': ['file.vala'],
     \ 'vera': ['file.vr', 'file.vri', 'file.vrh'],
     \ 'verilog': ['file.v'],
     \ 'verilogams': ['file.va', 'file.vams'],

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4251,
 /**/
     4250,
 /**/