MALLOC_DEBUG: Fix some misuses of free() when MALLOC_DEBUG is enabled.

* There were several places in ARI where an external library was mallocing
memory that must always be released with free().  When MALLOC_DEBUG is
enabled, free() is redirected to the MALLOC_DEBUG version.  Since the
external library call still uses the normal malloc(), MALLOC_DEBUG
complains that the freed memory block is not registered and will not free
it.  These cases must use ast_std_free().

* Changed calls to asprintf() and vasprintf() to the equivalent
ast_asprintf() and ast_vasprintf() versions respectively.
........

Merged revisions 400270 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@400271 65c4cc65-6c06-0410-ace0-fbb531ad65f3