don't use outputstr in the struct mansession, it's just

don't use outputstr in the struct mansession, it's just
an extra allocation on a path where we have way too many already.

Unfortunately the AMI-over-HTTP requires multiple copies,
because we need to generate a header, then the raw output to
an intermediate buffer, then convert it to html/xml, and
finally copy everything into a malloc'ed buffer because
that's what the generic_http_callback interface expects.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@48090 65c4cc65-6c06-0410-ace0-fbb531ad65f3