patch 9.0.0599: latexmkrc files are not recognized

Problem:    Latexmkrc files are not recognized.
Solution:   Use Perl filetype for latexmkrc files. (closes #11241)

runtime/filetype.vim

@@ -1026,6 +1026,9 @@ au BufNewFile,BufRead Kconfig,Kconfig.debug	setf kconfig
 " Lace (ISE)
 au BufNewFile,BufRead *.ace,*.ACE		setf lace
 
+" Latexmkrc
+au BufNewFile,BufRead .latexmkrc,latexmkrc	setf perl
+
 " Latte
 au BufNewFile,BufRead *.latte,*.lte		setf latte
 

src/testdir/test_filetype.vim

@@ -413,7 +413,7 @@ let s:filename_checks = {
     \ 'pccts': ['file.g'],
     \ 'pcmk': ['file.pcmk'],
     \ 'pdf': ['file.pdf'],
-    \ 'perl': ['file.plx', 'file.al', 'file.psgi', 'gitolite.rc', '.gitolite.rc', 'example.gitolite.rc'],
+    \ 'perl': ['file.plx', 'file.al', 'file.psgi', 'gitolite.rc', '.gitolite.rc', 'example.gitolite.rc', '.latexmkrc', 'latexmkrc'],
     \ 'pf': ['pf.conf'],
     \ 'pfmain': ['main.cf'],
     \ 'php': ['file.php', 'file.php9', 'file.phtml', 'file.ctp', 'file.phpt', 'file.theme'],

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    599,
 /**/
     598,
 /**/