Fix C89 build and small cleanup
Fixed bug #50175

0x and 0b prefix is now only handled if either no base is given
or if the base is 16 (0x) or 2 (0b). Always handling it is incorrect
because 0x and 0b are perfectly valid numbers in other bases.
Merge branch 'PHP-5.6'

Conflicts:
	ext/gmp/gmp.c