DESCRIPTION
===========
Buffer overflow is reported in a lot of code sections
spanning across server, client programs, Regex libraries
etc. If not handled appropriately, they can cause abnormal
behaviour.

ANALYSIS
========
The reported casea are the ones which are likely to result
in SEGFAULT, MEMORY LEAK etc.

FIX
===
- sprintf() has been replaced by my_snprintf() to avoid
buffer overflow.
- my_free() is done after checking if the pointer isn't
  NULL already and setting it to NULL thereafter at few
  places.
- Buffer is ensured to be large enough to hold the data.
- 'unsigned int' (aka 'uint') is replaced with 'size_t'
to avoid wraparound.
- Memory is freed (if not done so) after its alloced and
used.
- Inserted assert() for size check in InnoDb memcached
code (from 5.6 onwards)
- Other minor changes

(cherry picked from commit 3487e20959c940cbd24429afa795ebfc8a01e94f)