newlib 1.20.0

[tuxuser]

finish off integrating newlib 1.20.0

Major talking points now are - startup code - any additional syscalls we want to add

In terms of startup code, I propose a re-factor of startup_from_xell.S Most (if not all) of it can be moved into newlib itself, as crt0.s, which would allow the toolchain to be used easily without having to link against libxenon.

All startup_from_xell really does is set some known values to specific registers and set the stack pointer. Since the stack pointer is initialized by a linker script variable, it doesnt matter where this code is, since it will almost never change. Moving it to newlib seems the sane thing to do.

Any input on what you want to see in newlib 1.20.0 would be great