cjpeg: Fix buf overrun caused by bad bin PPM input

cjpeg: Fix buf overrun caused by bad bin PPM input

This extends the fix in 6709e4a0cfa44d4f54ee8ad05753d4aa9260cb91 to
include binary PPM/PGM files, thus preventing a malformed binary
PPM/PGM input file from triggering an overrun of the rescale array and
potentially crashing cjpeg.

Note that this issue affected only cjpeg and not the underlying
libjpeg-turbo libraries, and thus it did not represent a security
threat.

Thanks to @hughdavenport for the discovery.