This is an update to this patch to incorporate changes from reviews of 
earlier patches.

Keith

Changes since last version:
   - remove SAVE_SPEC stuff
   - struct linespec: use struct explicit_location instead of
     all those strings/line_offset.
   - Add PARSER_EXPLICIT and use it where needed
   - No need to "convert linespec to explicit" -- the parser
     now builds an explicit location of the parsed result.
   - move string constructions out of canonicalize_linespec and into
     its own function
   - update comments on grammar of linespecs: expr_spec is now
     no longer considered a linespec.
   - add explicit_to_string_internal and use it to implement
     explicit_location_to_string/explicit_location_to_linespec
   - new_explicit_location
   - remove explicit_to_event_location

ChangeLog
2014-05-29  Keith Seitz  <keiths@redhat.com>

	* breakpoint.c (create_overlay_breakpoint): Convert linespec
	into explicit location.
	(create_longjmp_master_breakpoint): Likewise.
	(create_std_terminate_master_breakpoint): Likewise.
	(create_exception_master_breakpoint): Likewise.
	(create_breakpoint): Update the SAVE_SPEC for explicit locations.
	(update_static_tracepoint): Convert linespec into explicit location.
	(location_to_sals): Save the string representation of the location
	for pending locations which were resolved.
	* linespec.c (enum offset_relative_sign): Move to location.h.
	(struct line_offset): Likewise.
	(struct linespec) <expression, expr_pc, source_filename>
	<function_name, label_name, line_offset>: Replace with ...
	<explicit>: ... this.
	<is_linespec>: New member.
	(PARSER_EXPLICIT): New accessor macro.
	(undefined_label_error): New function.
	(source_file_not_found_error): New function.
	(linespec_parse_basic): The parser result is now an explicit location.
	Use PARSER_EXPLICIT to access it.
	Use undefined_label_error.
	(canonicalize_linespec): Convert canonical linespec into explicit
	location.
	Move string representation of location to explicit_location_to_linespec
	and use it and explicit_location_to_string to save string
	representations of the canonical location.
	(create_sals_line_offset): Use PARSER_EXPLICIT to access the parser's
	explicit location result.
	(convert_linespec_to_sals): `ls' contains an explicit location.
	Update all references.
	(convert_explicit_location_to_sals): New function.
	(linespec_parse_basic): Use PARSER_EXPLICIT to access the parser
	result's explicit location.
	(linespec_state_constructor): Initialize is_linespec.
	Use PARSER_EXPLICIT.
	(linespec_parser_delete): Use PARSER_EXPLICIT to access the parser's
	result.
	(event_location_to_sals): For linespec locations, set is_linespec.
	Handle explicit locations.
	(decode_objc): 'ls' contains an explicit location now. Update all
	references.
	(symtabs_from_filename): Use source_file_not_found_error.
	* location.c (initialize_explicit_location): New function.
	(initialize_event_location): Initialize explicit locations.
	(copy_event_location): Handle explicit locations.
	(explicit_to_string_internal): New function; most of contents moved
	from canonicalize_linespec.
	(explicit_location_to_string): New function.
	(explicit_location_to_linespec): New function.
	(delete_event_location): Handle explicit locations.
	(event_location_to_string_const): Likewise.
	(event_location_empty_p): Likewise.
	* location.h (enum offset_relative_sign): Move here from linespec.h.
	(struct line_offset): Likewise.
	(enum event_location_type): Add EXPLICIT_LOCATION.
	(struct explicit_location): New structure.
	(struct event_location.u) <explicit>: New member.
	(EVENT_LOCATION_EXPLICIT): Define accessor macro.
	(explicit_location_to_string): Declare.
	(explicit_location_to_linespec): Declare.
	(initialize_explicit_location): Declare.