libagbabi 2.1.0

This is a clean-up & re-write of the entire project. We will be using GitHub Releases and Tags from now on.

Project changes

• New README.md and docs
• Provided minimal cross-build environments for standalone Meson and CMake builds

Clean-ups

• Removed C pre-processor use from assembly code
  • This includes the C/C++ style comments
• Moved some non-existant aeabi functions into agbabi
• Removed the fixed-point print formatting code
  • This will likely one day return in some other form

Re-writes

• Reversed some compiled & optimised assembly back into C code
  • GNU vector extensions are used to achieve optimal code-gen
• Removed DEVKITARM related macros
  • More explicit, compile-time feature detection is used instead

Additions

• Multiboot function added
  • This is a little experimental and may be buggy

Special thanks

@LunarLambda for Meson support