compiler: relocate ID encoding utilities to gofrontend

compiler: relocate ID encoding utilities to gofrontend

    Relocate the code that encodes/sanitizes identifiers to make them
    assembler-friendly, moving it from the back end to the front end; the
    decisions about when to encode an identifier and the calls to the
    encoding helpers now take place entirely in gofrontend.

    Reviewed-on: https://go-review.googlesource.com/33424

	* go-gcc.cc (char_needs_encoding): Remove.
	(needs_encoding, fetch_utf8_char, encode_id): Remove.
	(Gcc_backend::global_variable): Add asm_name parameter.  Don't
	compute asm_name here.
	(Gcc_backend::implicit_variable): Likewise.
	(Gcc_backend::implicit_variable_reference): Likewise.
	(Gcc_backend::immutable_struct): Likewise.
	(Gcc_backend::immutable_struct_reference): Likewise.
	* Make-lang.in (GO_OBJS): Add go/go-encode-id.o.

From-SVN: r242726