Make app_fax compatible with spandsp-0.0.6pre4

Prior to spandsp-0.0.6pre4 the t30_stats_t structure used a pages_transferred
integer to indicate the number of pages transferred (so far) during the fax
session.  The spandsp-0.0.6pre4 release removed the pages_transferred integer
and replaced it with two different integers - pages_tx and pages_rx.  This
revision uses the new integers for spandsp-0.0.6pre4 while maintaining backwards
compatibility for previous spandsp releases.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@177699 65c4cc65-6c06-0410-ace0-fbb531ad65f3