* 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/passwd.cc

@@ -13,6 +13,8 @@ details. */
 #include <pwd.h>
 #include <stdio.h>
 #include <errno.h>
+#include "dtable.h"
+#include "pinfo.h"
 
 /* Read /etc/passwd only once for better performance.  This is done
    on the first call that needs information from it. */