Add FPM support for <5.3.3

[mattheath]

FPM was only included with PHP from version 5.3.3 onwards. As raised in #16 the default configure options which included FPM caused compilation of 5.3.2 to fail, so FPM support was removed for this version of PHP.

Ideally FPM support would be added for 5.3.2 as otherwise this version cannot be used in projects which use FPM & Nginx.