#115 Only convert array into SplFixedArray if PHP >= 5.3 is available

@mturalenka please review and merge

The step where Browscap converts a regular array into a SplFixedArray for performance reasons is the only thing currently incompatible with PHP 5.2.
this line should also be in the 'if' statement.
also should be added else statement with `$tmp_user_agents_count = count($tmp_user_agents);`