Add MALLOC_DEBUG enhancements.

* Makes malloc() behave like calloc().  It will return a memory block
filled with 0x55.  A nonzero value.

* Makes free() fill the released memory block and boundary fence's with
0xdeaddead.  Any pointer use after free is going to have a pointer
pointing to 0xdeaddead.  The 0xdeaddead pointer is usually an invalid
memory address so a crash is expected.

* Puts the freed memory block into a circular array so it is not reused
immediately.

* When the circular array rotates out a memory block to the heap it checks
that the memory has not been altered from 0xdeaddead.

* Made the astmm_log message wording better.

* Made crash if the DO_CRASH menuselect option is enabled and something is
found.

* Fixed a potential alignment issue on 64 bit systems.
struct ast_region.data[] should now be aligned correctly for all
platforms.

* Extracted region_check_fences() from __ast_free_region() and
handle_memory_show().

* Updated handle_memory_show() CLI usage help.

Review: https://reviewboard.asterisk.org/r/2182/
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Merged revisions 376029 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 376030 from http://svn.asterisk.org/svn/asterisk/branches/10
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Merged revisions 376048 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@376049 65c4cc65-6c06-0410-ace0-fbb531ad65f3