[Ada] Wrong resolution of equality operator with overloaded operand

[Ada] Wrong resolution of equality operator with overloaded operand

This patch fixes a code generation error on an equality operation one of
whose operands is an overloaded call, and several equality operators are
visible. The resolution would succes but in some cases the wrong entity
was lwfton the equality node, leading to expansion with the wrong
interpretation.  If the equality operation is the operand of a negation,
the resolution of the negation must make direct use of the equality
resolution,

2019-07-09  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_res.adb (Resolve_Equality_Op): If the node was overloaded,
	set properly the entity to which the node has been resolved. The
	original entity is the first one found during analysis, and is
	not necessarily the resolved one.
	(Resolve_Op_Not): If the argument of negation is an overloaded
	equality operation, call its resolution directly given that the
	context type does not participate in overload resolution.

gcc/testsuite/

	* gnat.dg/equal7.adb, gnat.dg/equal7_pkg.adb,
	gnat.dg/equal7_pkg.ads: New testcase.

From-SVN: r273281