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/security.cc

@@ -29,6 +29,7 @@ details. */
 #include "sync.h"
 #include "sigproc.h"
 #include "pinfo.h"
+#include "security.h"
 
 extern BOOL allow_ntea;
 BOOL allow_ntsec = FALSE;