cel_pgsl: Add support for GMT timestamps

This patch adds a new option to cel_pgsl, "usegmtime", which causes timestamps
to be logged in GMT.

Review: https://reviewboard.asterisk.org/r/4571/

ASTERISK-23186 #close
Reported by: Rodrigo Ramirez Norambuena
patches:
  cel_pgsql.c_add_usegmtime2.patch submitted by Rodrigo Ramirez Norambuena (License 6577)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@434284 65c4cc65-6c06-0410-ace0-fbb531ad65f3