JBIGDecode doesn't check if the user provided buffer is large enough
to store the JBIG decoded image, which can potentially cause out-of-bounds
write in the buffer.
This issue was reported and analyzed by Thomas Dullien.

Also fixes a (harmless) potential use of uninitialized memory when
tif->tif_rawsize > tif->tif_rawcc

And in case libtiff is compiled with CHUNKY_STRIP_READ_SUPPORT, make sure
that whole strip data is provided to JBIGDecode()