Took the Xfree implementation (based on the same rewrite as the NDB one)
and added it instead of the current implementation.
Added a macro to make the calls to MD5 more streamlined. 

client/mysqlmanager-pwgen.c:
  Bug #42434: changed to call the macro
include/my_md5.h:
  Bug #42434: use the Xfree implementation
mysys/md5.c:
  Bug #42434: use the Xfree implementation
sql/item_strfunc.cc:
  Bug #42434: changed to call the macro
sql/table.cc:
  Bug #42434: changed to call the macro
tools/mysqlmanager.c:
  Bug #42434: changed to call the macro