the vararg list must be terminated with zero else 64bit machines may crash

the vararg list must be terminated with zero else 64bit machines may crash

On 64 bit systems, the integer 0 is 32 bits and the pointer 0 is 64 bits.
The upper 32 bits will not be cleared and the loop will never terminate.
Also add the RAZOR_SENTINEL __attribute__ ((__sentinel__(0))) on GCC4
so we catch where we get this wrong automatically.

This also fixes the new search functionality from James which was missed
in the merge.