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/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,