Description:
------------
While chking pcntl.c because of build errors on FreeBSD 6 and test failures on NetBSD 4, I spotted that SIG_UNBLOCK and SIG_SETMASK both have the same value as SIG_BLOCK.

Patch w/ test available here:

http://www.beccati.com/misc/php/pcntl_sig_constants_HEAD.diff

My karma prevents me from committing directly.

Reproduce code:
---------------
var_dump(SIG_BLOCK);
var_dump(SIG_UNBLOCK);
var_dump(SIG_SETMASK);

Expected result:
----------------
int(0)
int(1)
int(2)

Actual result:
--------------
int(0)
int(0)
int(0)