add running forward/backward along platform surfaces
stub out _drawenemies
in 01_plotonscreen, view[] now goes to the end of RAM, not end of RAM - 2.  we aren't currently using the stack.
09_garbage:  sometimes, from some views, garbage gets rendered.  this tests for platform widths specified that are out of the 0-19 range.  those five bits can hold 0-31.
small bit of diagnostics in 08_momentum
update personal notes/todo
add 'enemy' excursion to the 'platforms' render kernel; execution is sent there from 'renderpump' when the foreground color comes back as 0.  that updates the sprite pattern buffer and width.
delay ending VBLANK till as far near the end of scanline 37 as we go before doing a VSYNC.
changed 'platformcolors' entries for %111xxxxx to return 0 to trigger the call to 'enemy' rather than %000xxxxx.