[Critical] Fix socket timeout error when connecting over high-latency network

This commit https://github.com/pdezwart/php-amqp/commit/5c87537cb81cbe2a1e0ccf2f76cedb7ef6a182b6 from https://github.com/pdezwart/php-amqp/pull/102 in addition to fix not freed memory when timeout used also breaks completely connection when no connection timeout being used. To prevent timeout logic `timeval` structure should be set to `NULL`, not filled with zeros.

So without this changes no one can connect to remote server while connection timeout will be used but set to `0`.

//cc @jpauli