This patch adds missing ECF_NOTHROW flags to the vectorisable
integer internal functions.

2017-08-17  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	* internal-fn.def (CLRSB, CLZ, CTZ, FFS, PARITY, POPCOUNT): Add
	missing ECF_NOTHROW flags.

From-SVN: r251155