Improvements in SC_Process and other lv2 syscalls

* Splitted the file in SC_Process.h and SC_Process.cpp.
* Some argument data types modified on sys_process_* functions.
* Implemented sys_process_get_number_of_object and sys_process_get_id.
* Added dummy versions of other sys_process_* functions based on the old
SysCalls::lv2Process* code (which I deleted).
* Improved BE <-> LE comparisons on SC_Mutex, SC_Lwmutex and SC_Lwcond.
* Updated some SC_Memory functions to use mem_ptr_t<T>.

NOTE: There are probably better ways to get the active objects that
don't imply creating a new data type filled with std::set<u32>'s.

TODO: For some types, the corresponding std::set<u32> isn't being
updated when an object is created/destroyed. I'll take care of this
soon.