LIKE AND CONVERT

Valgrind complains uninitialized value in my_wildcmp_mb_impl() and
my_wildcmmy_wildcmp_8bit_impl(). This is because pointer steps to byte
beyond string length. And this pointer is actually not necessary to get
comparison result.

Fix:
Change the my_wildcmp_XX's loop condition to avoid reading uninitialized
memory.

wild_compare_full() only works for null-terminated string. Also change it
to be safe for tight bound string.

Change-Id: Ie8920c8a3287f79297fae3aeeabd48c537da6bdf