RASTLIB: add CMake file.
RASTLIB: do not reserve additional space for unforeseen Rastlib functions.
RASTLIB: make rastcalls take Pixel *pixbufs and unsigned widths and heights.
RASTLIB: fix prototypes and unused variables.
RASTLIB: make pj_get_<raster>_lib functions return a Rastlib.
RASTLIB: fix signed/unsigned mismatches and casts.