Mapped location support
	* back_end.adb (Call_Back_End): Pass information about source
	files instead of units to gigi.
	* gigi.h (struct File_Info_Type): New.
	(gigi): Rename and change type of number_units parameter, change
	type of file_info_ptr parameter.
	* trans.c (number_files): New global variable.
	(gigi): Rename and change type of number_units parameter, change
	type of file_info_ptr parameter.
	If mapped location support is enabled, create the isomorphic mapping
	between source files and line maps.
	(Sloc_to_locus): If mapped location support is enabled, translate
	source location into mapped location.
	(annotate_with_node): Rename into set_expr_location_from_node.
	Call set_expr_location instead of annotate_with_locus.
	(Pragma_to_gnu): Adjust for above change.
	(Loop_Statement_to_gnu): Likewise.
	(call_to_gnu): Likewise.
	(Handled_Sequence_Of_Statements_to_gnu): Likewise.
	(gnat_to_gnu): Likewise.
	(add_stmt_with_node): Likewise.
	(add_cleanup): Likewise.
	* utils.c (gnat_init_decl_processing): Do not set input_line.

From-SVN: r128839