Bug#17667: An attacker has the opportunity to bypass query logging.

This adds a new, local-only printf format specifier to our *printf functions
that allows us to print known-size buffers that must not be interpreted as 
NUL-terminated "strings."

It uses this format-specifier to print to the log, thus fixing this 
problem.


include/my_sys.h:
  Add prototype for my_memmem() .
mysys/Makefile.am:
  Add reference to new file, my_memmem.c
mysys/mf_iocache2.c:
  Add a "%.1234b" and "%.*b" percent-code.  It takes a width, just like "%s", 
  but unlike the string-indicator, it requires the width and doesn't stop printing
  at NUL characters.
  
  Also, simplify the code a bit.
  
  TODO:  This code should be unified with the strings/my_vnsprintf.c code in 
  the future.
sql/sql_parse.cc:
  The query is not a C-string, but is a sized buffer, containing any character 
  at all, which may include NUL characters.
strings/my_vsnprintf.c:
  Add a "%.1234b" and "%.*b" percent-code.  It takes a width, just like "%s", 
  but unlike the string-indicator, it requires the width and doesn't stop printing
  at NUL characters.
tests/Makefile.am:
  We may need some of our local functions.
tests/mysql_client_test.c:
  Add a "%.1234b" and "%.*b" percent-code.  It takes a width, just like "%s", 
  but unlike the string-indicator, it requires the width and doesn't stop printing
  at NUL characters.
mysql-test/t/mysql_client_test.opt:
  New BitKeeper file ``mysql-test/t/mysql_client_test.opt''
  
  Add '--log' server parameter.
mysys/my_memmem.c:
  New BitKeeper file ``mysys/my_memmem.c''
  
  Implement memmem, a black-box work-alike of the GNU memmem(), which functions
  like strstr() but for arbitrary blocks of memory.