[PR89528] reset debug uses of return value when dropping dead RTL call

[PR89528] reset debug uses of return value when dropping dead RTL call

When we remove an RTL call, we wouldn't clean up references to the
return value of the call in debug insns.  Make it so that we do.

for  gcc/ChangeLog

	PR debug/89528
	* valtrack.c (dead_debug_insert_temp): Reset debug references
	to the return value of a call being removed.

for  gcc/testsuite/ChangeLog

	PR debug/89528
	* gcc.dg/guality/pr89528.c: New.

From-SVN: r270389