* include/sys/cygwin.h (CW_SETERRNO): Define.

* external.cc (CW_SETERRNO): Implement.
* include/cygwin/version.h: Bump CYGWIN_VERSION_API_MINOR to 192 to reflect the
above change.
* path.cc (path_prefix_p): Treat X: as equivalent to x:.
* mkglobals_h: Remove unneeded #define.
* spawn.cc (spawn_guts): Avoid overly wordy initialization to zero.

winsup/cygwin/mkglobals_h

@@ -18,7 +18,6 @@ print <<PRELUDE,$_,"#endif /*_GLOBALS_H*/\n";
 /* $target - Autogenerated from @argv.  Look there for comments. */
 
 #ifndef _GLOBALS_H
-#define _GLOBALS_H 1
 PRELUDE
 close $target_fd;
 sub munge($) {