Piotr Jaroszyński: Usermode debugging under Linux

I have finished the stdlib-free implementation. It's available on the linux branch. Most of the new stuff is in these commits:

• [linux] Add linuxprefix
• [linux] Add linux_syscall
• [linux] Add most of the linux api
• [linux] Add linux_realloc

I have also done some refactoring along the way, most notably the command line argument handling has been changed to not require any core/main.c changes.

• [linux] Add command line arguments for network setup

The implementation linking to stdlib has been moved to a separate linuxlibc PLATFORM and is now on its own linuxlibc branch.

Details of the implementation will follow in the notes soon.