* cygprops.h: Use #pragma once.

* mkglobals_h: Ditto for generated globals.h file.
* globals.cc: Use specific NO_GLOBALS_H flag to control inclusion of globals.h.
* winsup.h: Honor NO_GLOBALS_H to control inclusion of globals.h.  Make
clear_procimptoken extern inline so that it is only defined when needed.

winsup/cygwin/winsup.h

@@ -298,9 +298,10 @@ extern "C" char _data_start__, _data_end__, _bss_start__, _bss_end__;
 extern "C" void (*__CTOR_LIST__) (void);
 extern "C" void (*__DTOR_LIST__) (void);
 
-#if !defined(_GLOBALS_H)
+#ifndef NO_GLOBALS_H
 #include "globals.h"
-inline void clear_procimptoken ()
+
+extern inline void clear_procimptoken ()
 {
   if (hProcImpToken)
     {
@@ -309,6 +310,5 @@ inline void clear_procimptoken ()
       CloseHandle (old_procimp);
     }
 }
-#endif
-
+#endif /*NO_GLOBALS_H*/
 #endif /* defined __cplusplus */