Mass rename `explicit' -> `explicit_loc'.

Mass rename `explicit' -> `explicit_loc'.

BuildBot reminded me that "explicit" is a reserved keyword in C++.
This patch simply renames all the (illegal) uses of "explicit". This should
fix the build errors with --enable-build-with-cxx bots.

gdb/ChangeLog

	* break-catch-throw.c (re_set_exception_catchpoint) Rename
	reserved C++ keyword "explicit" to "explicit_loc".
	* breakpoint.c (create_overlay_event_breakpoint)
	(create_longjmp_master_breakpoint)
	(create_std_terminate_master_breakpoint)
	(create_exception_master_breakpoint, update_static_tracepoint):
	Rename reserved C++ keyword "explicit" to "explicit_loc".
	* completer.c (collect_explicit_location_matches)
	(explicit_location_completer): Rename reserved C++ keyword
	"explicit" to "explicit_loc".
	* linespec.c (struct linespec) <explicit>: Rename to "explicit_loc".
	(canonicalize_linespec, create_sals_line_offset)
	(convert_linespec_to_sals, convert_explicit_location_to_sals)
	(event_location_to_sals, decode_objc): Rename reserved C++ keyword
	"explicit" to "explicit_loc".
	* location.c (struct event_location) <explicit>: Rename to
	"explicit_loc".
	(initialize_explicit_location, new_explicit_location)
	(explicit_location_to_string_internal, explicit_location_to_linespec):
	Rename reserved C++ keyword "explicit" to "explicit_loc".
	* location.h (explicit_location_to_string)
	(explicit_location_to_linespec, initialize_explicit_location)
	(new_explicit_location): Rename reserved C++ keyword "explicit"
	to "explicit_loc".
	* mi/mi-cmd-break.c (mi_cmd_break_insert_1): Rename reserved C++
	keyword "explicit" to "explicit_loc".