err_vars.ads, [...]: Eliminate the vestigial Internal_Source_File and the Internal_So...

err_vars.ads, [...]: Eliminate the vestigial Internal_Source_File and the Internal_Source buffer.

2017-04-25  Bob Duff  <duff@adacore.com>

	* err_vars.ads, fmap.adb, fmap.ads, comperr.adb, fname-sf.adb,
	types.adb, types.ads, types.h, sinput-l.adb, targparm.adb,
	errout.adb, sinput.adb, sinput.ads, cstand.adb, scn.adb,
	scn.ads, gnatls.adb: Eliminate the vestigial Internal_Source_File and
	the Internal_Source buffer. This removes the incorrect call to "="
	the customer noticed.
	Wrap remaining calls to "=" in Null_Source_Buffer_Ptr. We
	eventually need to eliminate them altogether. Or else get rid
	of zero-origin addressing.

From-SVN: r247234