Reads a portable graymap as input. Produces a Lisp Machine bitmap as output.
This is the file format read by the tv:read-bit-array-file function on TI Explorer and Symbolics lisp machines.
Given a pgm (instead of a pbm) a multi-plane image will be output. This is probably not useful unless you have a color lisp machine.
Output width is always rounded up to the nearest multiple of 32; this might not always be what you want, but it probably is (arrays which are not modulo 32 cannot be passed to the Lispm BITBLT function, and thus cannot easily be displayed on the screen).