compute discriminator info for overrides

compute discriminator info for overrides

In some cases of overriding or resetting locations, we might retain
discriminator info from earlier locations, when we should take
discriminator information from the overriding location or reset it.

for  gcc/ChangeLog

	* final.c (compute_discriminator): Declare.  Renamed from...
	(maybe_set_discriminator): ... this.  Set and return a local.
	(override_discriminator): New.
	(final_scan_insn_1): Set it.
	(notice_source_line): Adjust.  Always set discriminator.

From-SVN: r266349