mod_spandsp: add start_tone_detect/stop_tone_detect app and api commands for tone and cadence detection (MODAPP-378)

add endpoint-name conf parameter represents endpoint name.
fix GK registration retrying in case of registration reject.
fix double DTMF hadling for examle in case dtmf-relay h245-signal h245-alphanumeric on cisco dial-peer.
fix crash on module unloading.

mod_spandsp: improve duplicate digit detection and add 'min_dup_digit_spacing_ms' channel variable for use with the dtmf detector (FSMOD-45)

The 'day' field is the month day (and not year day).

Fix MODSKINNY-4 and MODSKINNY-7

thanks to Frank Seesink on MODSKINNY-6

declaring some variables "extern" thanks to Peter Olsson

Fix MODSKINNY-6: Build still fails on OS X (even after last changes)