patch 9.0.0599: latexmkrc files are not recognized

Problem:    Latexmkrc files are not recognized.
Solution:   Use Perl filetype for latexmkrc files. (closes #11241)
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 3b3d9a5..43f9664 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -413,7 +413,7 @@
     \ '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'],
diff --git a/src/version.c b/src/version.c
index 515be0b..bfc057b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    599,
+/**/
     598,
 /**/
     597,