This change only affects GNATprove backend, where it avoids spurious
errors on missing ALI files for units indirectly withed from the current
unit and processed as part of a different .gpr project.

No test provided, because only GNATprove is affected.

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-09-17  Piotr Trojanek  <trojanek@adacore.com>

gcc/ada/

	* ali.ads: Fix casing in comment.
	* ali-util.ads, ali-util.adb (Read_Withed_ALIs): Remove
	Ignore_Errors parameter; it was only set to non-default value of
	True when running in GNATprove_Mode and wrongly reset to False
	when calling this routine recursively. Now in GNATprove mode we
	want it to be always True, so in fact it is equivalent to
	GNATProve_Mode flag itself (which was already used in this
	routine).