* winsup.h: Split out dtable definitions into separate header file.

* dtable.h: New file.
* sigproc.h: Eliminate pinfo.h usage here.  Use it in source files that need
it.

winsup/cygwin/heap.cc

@@ -10,6 +10,7 @@ details. */
 
 #include "winsup.h"
 #include <errno.h>
+#include "pinfo.h"
 
 #define brksize ((char *) user_data->heaptop - (char *) user_data->heapbase)
 #define brk (user_data->heapptr)