FIX: disable SIGPIPE on platforms w/SO_NOSIGPIPE

The DISABLE_SIGPIPE_WITH_SETSOCKOPT preprocessor define got deleted the
os-layer socket functions were moved to amqp_socket.c. This fixes that.
FIX: force correct timer precision on Mac OS X
Add partial support for heartbeats in wait_frame
Add support for heartbeats in amqp_basic_publish

Check heartbeats when doing basic.publish. Do this by doing a recv on
the socket.
Code clarity improvements in heartbeat handling
listen to multiple routing keys separated by commas
OpenVMS MMS build system

Tested on OpenVMS v8.3 - Alpha. Likely to work on IA based systems as well