Add new syscalls

Hello,
I finally took the time to commit and push the changes on my fork's local tree, adding some new syscalls to my fork. Some syscalls were added based on information from Simon Lothar's docs and some, like CLIP_Store and the file transfer ones, were found/documented by him on my request (see http://www.casiopeia.net/forum/viewtopic.php?f=22&t=1663 and http://www.casiopeia.net/forum/viewtopic.php?f=22&t=1577 )

As I did this, I found out there were many other syscalls on my fork that were not on the official libfxcg, so I took the time to cherry-pick all my changes related to syscalls, into a single pull request.

I tried to make merging as easy as possible by cherry-picking the specific commits where I added the syscalls into a specific branch, against a updated upstream. There was a problem related to the SetQuitHandler syscall, turns out my fork had it under a different (Simon's) name, CallbackAtQuitMainFunction. In this pull request I left the original libfxcg name and I will proceed to update my fork and my project's source code to use it. Assuming I managed to not mess up, this pull request doesn't break compatibility with any code relying on the original libfxcg.

I checked the end result and unless you have any objection related to the syscalls' names or the files where I put their headers, everything seems fine. I'm sorry for pulling so much in at once; for months, I didn't realize how far my fork was from the official one, and even the changes between my local, non-committed tree and my fork were more than expected.