Verify whether the created buffer was actually large enough to hold the expanded...

Verify whether the created buffer was actually large enough to hold the expanded value.

For certain types of queries, where the size of the substituted query was much
larger than the template, it was possible for the substitution buffer to be too
small.  This is only an issue in 1.6.1, as previously we used a static buffer
anyway, and we have a substitution routine in 1.6.2 forward that automatically
sizes itself appropriately to handle larger expansions.

(closes issue #17006)
 Reported by: viniciusfontes
 Patches:
       20100311__issue17006.diff.txt uploaded by tilghman (license 14)
 Tested by: tilghman

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.1@251875 65c4cc65-6c06-0410-ace0-fbb531ad65f3