patch 9.0.1668: PEM files are not recognized

Problem:    PEM files are not recognized.
Solution:   Add patterns to match PEM files. (closes #12582)
diff --git a/src/version.c b/src/version.c
index 5c83d40..d18ecc1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1668,
+/**/
     1667,
 /**/
     1666,