Break out more header info into separate files. Use appropriate header files

throughout.
* shared.h: Remove.
* cygwin_version.h: New file.
* delqueue.h: New file.
* environ.h: New file.
* host_dependent.h: New file.
* perprocess.h: New file.
* registry.h: New file.
* security.h: New file.

winsup/cygwin/heap.h

@@ -8,6 +8,8 @@ This software is a copyrighted work licensed under the terms of the
 Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
 details. */
 
+#include "perprocess.h"
+
 /* Heap management. */
 void heap_init (void);
 void malloc_init (void);