gccrs: Merge Gcc_linemap into Linemap

gccrs: Merge Gcc_linemap into Linemap

gcc/rust/ChangeLog:

	* rust-linemap.cc
	(class Gcc_linemap): Remove.
	(Gcc_linemap::start_file): Move to...
	(Linemap::start_file): ... here.
	(Gcc_linemap::to_string): Move to...
	(Linemap::to_string): ... here.
	(Gcc_linemap::stop): Move to...
	(Linemap::stop): ... here.
	(Gcc_linemap::start_line): Move to...
	(Linemap::start_line): ... here.
	(Gcc_linemap::get_location): Move to...
	(Linemap::get_location): ... here.
	(rust_get_linemap): Use Linemap.
	* rust-linemap.h
	(Linemap::in_file_): New field from Gcc_linemap.
	(Linemap::Linemap): Initialize in_file_.
	(Linemap::~Linemap): Make non-virtual.
	(Linemap::start_file): Likewise.
	(Linemap::start_line): Likewise.
	(Linemap::get_location): Likewise.
	(Linemap::stop): Likewise.
	(Linemap::to_string): Likewise.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>