php53-mongo: update to 1.6.4.
php53-mongo: update to 1.6.4.

Closes #1597.

Signed-off-by: Alan Ivey <ee249fd9166eccef852f50ca0cbb6ff8665afe99@gmail.com>

TomK/homebrew-php,ablyler/homebrew-php,dguyon/homebrew-php,philcook/homebrew-php,mkalkbrenner/homebrew-php