Add missing primitive implementation for the plain interpreter.
To start up:
$ sdl-csi tng.scm
You don't need to compile to .so yet - the interpreted versions work
fine and we don't yet need the speed.
Roadmap:
image.scm - image save/load code
interp.scm - (empty) will contain bytecode interpreter
kernel-methods.scm - primitive definitions
kernel.scm - image bootstrap code, primitive table, method glue
macros.scm - macros used by more than one file
morph.scm - (unfinished) will contain morphic-like UI definitions
oo.scm - core object structures and dispatch code
root-hooks.scm - include file defining global image structures
sdl-events.scm - include file defining available SDL event types
sugar.scm - (unfinished) aborted attempt at a macro-based parser
tng.scm ******* - MAIN FILE - LOAD THIS INTO sdl-csi
ui.scm - SDL-interface definitions + main loop
util.scm - various utilities