Asterisk HA patches

The following may be applied to Asterisk patch_1.4.22.2

All code is copyright © 2008, 2009 Telecom Logic, LLC., and may be redistributed freely.

Essential changes:

cdr.h - double the size of AST_MAX_USER_FIELD so we can cram more data into CDRs.

chan_sip.c - added caching of negative realtime query results to improve database performance; send manager events on any sip message that causes ast_queue_control() to be called; in sip_send_all_registers set min/max regspacing to 100/500 ms.

channel.h - add codec/frames info to Hangup manager event; squelch Newchannel, Newcallerid manager events.

asterisk.c - sim calls + bandwidth + load monitoring thread that logs to astmon.log.

dsp.c - improved DTMF detection performance over noisy GSM channels without increasing false-positives.

res_odbc.c - adds ODBC failover capability - secondary database can be specified in config.

res_config_odbc.c - added "AND (systemname IS NULL OR systemname='%s')" to all static-realtime queries so we can replicate all tables including the config table to all database nodes, plus am now able to have asterisk failover it's odbc connection to another db -- because now each asterisk instance knows it's own node name ('systemname' in asterisk.conf) it can pull out config rows that shouldn't be read by others .. e.g. outbound registrations or zap channels..