[Ada] Link error due to negated intrinsic comparison

[Ada] Link error due to negated intrinsic comparison

This patch corrects the resolution of operator "not" when the expression
being negated is an equality operator to prevent the transformation of
an intrinsic equality operator into a function call.

2019-07-11  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* sem_res.adb (Resolve_Op_Not): Do not rewrite an equality
	operator into a function call when the operator is intrinsic.

gcc/testsuite/

	* gnat.dg/equal9.adb: New testcase.

From-SVN: r273385