* 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/path.cc

@@ -81,6 +81,7 @@ details. */
 #include <errno.h>
 #include <ctype.h>
 #include <winioctl.h>
+#include "pinfo.h"
 
 static int normalize_win32_path (const char *cwd, const char *src, char *dst);
 static char *getcwd_inner (char *buf, size_t ulen, int posix_p, int with_chroot);