patch 8.0.1252: incomplete translations makefile for MinGW/Cygwin

Problem:    Incomplete translations makefile for MinGW/Cygwin.
Solution:   Add missing source files.  Make it work with msys2's bash. (Ken
            Takata)
diff --git a/src/version.c b/src/version.c
index 552de77..59ecefe 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1252,
+/**/
     1251,
 /**/
     1250,