Consistency for opcache.max_accelerated_files

From README

	The number is actually the first one in the following set of prime
	numbers that is bigger than the one supplied: { 223, 463, 983, 1979, 3907,
	7963, 16229, 32531, 65407, 130987, 262237, 524521, 1048793 }. Only numbers

Make default value + opcache.ini consistent with this
(so 3907 instead of 2000, as this is the real value used)

Also report the real value in opcache_get_configuration.