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/window.cc

@@ -14,10 +14,13 @@ details. */
 #include <sys/time.h>
 #include <stdlib.h>
 #include <errno.h>
+#include <signal.h>
 #include <limits.h>
 #include <wingdi.h>
 #include <winuser.h>
 #include "cygerrno.h"
+#include "perprocess.h"
+#include "security.h"
 
 static NO_COPY UINT timer_active = 0;
 static NO_COPY struct itimerval itv;