patch 8.1.1111: it is not easy to check for infinity

Problem:    It is not easy to check for infinity.
Solution:   Add isinf(). (Ozaki Kiichi, closes #3787)
diff --git a/src/version.c b/src/version.c
index 38a7683..9c237e5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1111,
+/**/
     1110,
 /**/
     1109,