Made some changes to the I/O stream library for memory streams.
There were a number of potential problems due to the possibility
of integer overflow.
Changed some integral types to the larger types size_t or ssize_t.
For example, the function mem_resize now takes the buffer size parameter
as a size_t.
Added a new function jas_stream_memopen2, which takes a
buffer size specified as a size_t instead of an int.
This can be used in jas_image_cmpt_create to avoid potential
overflow problems.

Added a new function jas_deprecated to warn about reliance on
deprecated library behavior.