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/dll_init.cc

@@ -9,8 +9,10 @@ details. */
 #include "winsup.h"
 #include <stdlib.h>
 #include "exceptions.h"
-#include "dll_init.h"
 #include "cygerrno.h"
+#include "perprocess.h"
+#include "dll_init.h"
+#include "environ.h"
 
 extern void __stdcall check_sanity_and_sync (per_process *);