patch 8.1.1174: cannot build with Ruby 1.8

Problem:    Cannot build with Ruby 1.8. (Tom G. Christensen)
Solution:   Include ruby/st.h. (Ozaki Kiichi, closes #4257)
diff --git a/src/version.c b/src/version.c
index bc12aae..54c15f3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1174,
+/**/
     1173,
 /**/
     1172,