New stability fixes after testing huge software

For most of this project, I've only tested tiny 6kb binaries through USB.
Some new hacks allowed me to run Doom on my camera, which is around 10mb.

Doom port will be released on April first (for X-A2 only).

This is a huge step for testing the stability of this hack, and making sure
everything is POSIX compliant. More integration with the Frontier operating system
will follow.

Fix stubs, add some probably

Some etc probably moved around for xf1, but add FIRM_URL
for regression testing, and stub.h was improved also to allow
trampoline funcs to be deleted by linker