Merge branch 'rj/no-xopen-source-for-cygwin' into maint

Code cleanups.

* rj/no-xopen-source-for-cygwin:
  git-compat-util.h: remove redundant code

git-compat-util.h

@@ -164,16 +164,10 @@
 typedef long intptr_t;
 typedef unsigned long uintptr_t;
 #endif
-#if defined(__CYGWIN__)
-#undef _XOPEN_SOURCE
-#include <grp.h>
-#define _XOPEN_SOURCE 600
-#else
 #undef _ALL_SOURCE /* AIX 5.3L defines a struct list with _ALL_SOURCE. */
 #include <grp.h>
 #define _ALL_SOURCE 1
 #endif
-#endif
 
 /* used on Mac OS X */
 #ifdef PRECOMPOSE_UNICODE