add switch_socket_waitlist for waiting on multiple sockets and abstract it to poll and select so windows can use it too

FS-6686 #resolve #comment increased the timeout to 30 to accomidate situations where the engine takes longer to pick an IP

FS-6682: fix arg order on switch_channel_export_variable called from switch_channel_export_variable_printf #resolve

use final_delivery variable in chat plan to indicate that you do not want to deliver the message to its intended recipient because you have already pre-empted the message

Changes by Ryan Lantzer <lantzer@mst.edu> to correct the generation of
line_instance value in outbound ringer requests as part of trying to
diagnose 79x1 series phones not using the correct ring tone for
calls coming into secondary lines.

tweak timeout a little as it was changing to 1000000 on the 5th try on return from switch_interval_time_from_timeval on OpenBSD

fix resampler issue caused by refactoring impacting audio quality of resampled calls in the conference

For some reason these files would get marked as modified
just after a fresh clone on Linux

mod_prefix is an in-memory data store optimized for fast lookups
according to the longest prefix match (LPM) rule.

Tables of key-value string pairs in JSON format can be loaded at
startup via configuration and at runtime via the API.

The implementation uses a bitwise trie (aka binary prefix tree), so
arbitrary string keys are supported.