printer.lisp: better preserve proto names

[proto -> lisp]
1) Do case-sensitive comparisons between the name we have and the name
   we would derive from #'CLASS-NAME->PROTO. Case matters.

2) Do not downcase :name options when we're outputting them to a .lisp
   file. Again, case matters.

3) Preserve names for PROTOBUF-SERVICEs, as necessary.

4) Preserve names, input-names, and output-names for PROTOBUF-METHODs,
   as necessary.