loaders: JPG: Fix two bugs.

* The fill_input_buffer() should use return from read not the buffer size

* The skip_input_data() should at least print warning if Seek failed

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
spiv: Fix -t for zip container.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: PNG: Use GP_IOFill() to fill whole buffer

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
spiv: Show pixel type in info.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
libs: loaders: Create Zlib decompression stream

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
loaders: zip: Make use of Zlib stream.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>