[RFC] Change last_annotated_node from tree to location_t *

[Andrew Pinski <pinskia at physics dot uc dot edu>]

The problem here is that last_annotated_node keeps the full tree node 
in GC
which means that we can leak the whole function body and all the basic 
blocks
or the whole function tree depending on if the tree was in an unused 
static
function or in a function which goes though optimization.  This fixes 
the
problem by only keep tracking of the location_t instead.  This code 
would
go away when non USE_MAPPED_LOCATION mode goes away but that looks like
it is not going away for 4.1.0 which is sad.  The only thing blocking
USE_MAPPED_LOCATION now is the Ada front-end and has been for now 6 
months.

This was ___not___ bootstrapped as I don't have time right now and I
wanted to double check if this is the correct way to fix this problem.

Thanks,
Andrew Pinski

ChangeLog:

	* tree.c (last_annotated_node): Change type to location_t*.
	(annotate_with_file_line): Reflect the change of
	last_annotated_node type.

Attachment: t.diff.txt
Description: Text document