Cleanup of code base.

* scrypt_pickparams is no longer present on windows builds.
* Module dependancies declared.
* Swapped from using php_error to php_error_docref and drop errors down to warnings.
* Swapped form using emalloc to safe_emalloc
* Fixed a bug where R & P where being clamped to 64bits, not 32bits.
* Changed the clamp functions to output errors via an error parameter.
* Using the RETURN_FALSE macro rather than RETURN_BOOL(0)

Fixes #8 - Fails scrypt_pickparams test