Enable mcrypt, intl and exif support in PHP
php: Add xsl optional support

Use an override with xsl = true to enable xsl support in php.
php: Add mcrypt optional support

Use an override with mcrypt = true to enable libmcrypt support in php.
The --disable-posix-threadsds mcrypt build option was required by php.
php: Add zip and optional bz2 support

Use the overload bz2 = true to enable bz2 support for php.
zip support is enabled by default as it doesn't require any library.
Remove misconfigured mcrypt support
Merge remote-tracking branch 'bbenoist/phpfix' into php

Conflicts:
	pkgs/development/interpreters/php/5.3.nix
Merge remote-tracking branch 'upstream/master' into php
Merge pull request #276 from aforemny/php

Enable intl and exif support in PHP