patch 7.4.976

Problem:    When compiling Vim for MSYS2 (linked with msys-2.0.dll), the Win32
            clipboard is not enabled.
Solution:   Recognize MSYS like CYGWIN. (Ken Takata)

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    976,
 /**/
     975,
 /**/