ID member m_flags has been replaced with m_type, which stores the type
of the object referenced by the ID and added std::set<IDType> to the ID
manager to group relevant IDs in order to use them later in some
lv2/sys_process functions and the Kernel Explorer.
Reasons: 1) It's unsafe - we cannot guarantee that address is still good
while it is used. 2) It's wrong in many modules which are usually just
compare pointer with zero.
* Replace `int` with `s32` as return type for syscalls.
* Renamed `SC_Something.*` files with the proper lv2 name
`sys_something.*`.
* Moving away from the lv2, those functions and folders that doesn't
correspond to lv2 functions. E.g. module functions from sys_io,
sysPrxForUser, cellGcmSys.
* Splitted some files (memory -> memory+mmapper) and merged other ones
(event+event_flag ->event, spu+spu_thread -> spu), according to common
sense, PSDevWiki docs, and checking firmware files.
* Removed external functions from `SysCalls.h`.
NOTE: What should we do about: cellGcmCallback? It's not a lv2 syscall
but it appears on the sc_table and it is actually called in games. Is
this some kind of hack?
