Improved image dec. modules & New dummy modules

* Improved image decoding modules:
- Fixed error that appeared after last commit (eebe859f83).
- Changed some functions to use the mem*_t classes.
- Implemented cell*DecSetParameter.

* Created new dummy modules for sys_net (0x0000), sys_http (0x0001),
cellHttpUtil (0x0002) and cellSsl (0x0003).