jpeg2000: tag_tree_size: replace check by assert

This function is never called with values large enough for the
error condition to occur

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
jpeg2000: remove unneeded variable initialization

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
jpeg2000: merges quantization fixes from j2k

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
jpeg2000: remove unneeded casts

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
jpeg2000/j2k: merge j2k/jpeg2000.c/h

Now only j2kdec / jpeg2000dec.c remain

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>