Fixes#123. Guards `_PSP_FW_VERSION` references with `#if defined()` to avoid the SDK headers returning warnings when compiling modules with the `-Wundef` cflag.
Updated fourth argument of decompression routines.
When not NULL, the routines will store a pointer to the next unprocessed compressed byte (src + n_compressed_bytes_processed).
This can be useful to implement stream-based decompression, calculating number of processed compressed bytes, etc.
