Get rid of Closer MOP & Trivial Gray Streams deps

[aartaka]

Graven Image is intended to be a drop-in portability library, but dependence on Closer MOP and Trivial Gray Streams makes the installation much more involved than it should be for a real portability library.

• [x] Remove Closer MOP dependency. Reimplement/import these:
  • [x] generic-function-methods
  • [x] method-generic-function
  • [x] generic-function-lambda-list & method-lambda-list
  • [x] generic-function-method-combination
  • [x] class-slots
  • [x] slot-definition-name
  • [x] class-direct-superclasses
• [x] Trivial Gray Streams:
  • [x] fundamental-character-output-stream
  • [x] stream-line-column
  • [x] stream-write-char