Cygwin: clean error mapping

- Move definition of windows to POSIX error mapping struct into
  cygerrno.h
- Move declaration of winsock errno functions to cygerrno.h
- Input to error mapping functions is DWORD

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/cygerrno.h

@@ -11,6 +11,13 @@ details. */
 #include <errno.h>
 #include "regparm.h"
 
+struct errmap_t
+{
+  DWORD w;		 /* windows version of error */
+  const char *s;	 /* text of windows version */
+  int e;		 /* errno version of error */
+};
+
 void __reg3 seterrno_from_win_error (const char *file, int line, DWORD code);
 void __reg3 seterrno_from_nt_status (const char *file, int line, NTSTATUS status);
 int __reg2 geterrno_from_win_error (DWORD code = GetLastError (), int deferrno = 13 /*EACCESS*/);
@@ -34,6 +41,9 @@ __set_errno (const char *fn, int ln, int val)
 }
 #define set_errno(val) __set_errno (__PRETTY_FUNCTION__, __LINE__, (val))
 
+void __reg2 __set_winsock_errno (const char *fn, int ln);
+#define set_winsock_errno() __set_winsock_errno (__FUNCTION__, __LINE__)
+
 #define get_errno()  (errno)
 extern "C" void __stdcall set_sig_errno (int e);