Renamed CodeGen to ExternalTool.
Moved logger constants from asmjit namespace to asmjit::Logger.
Moved AssemblerFeature constants from asmjit namespace to asmjit::Assembler.
Added noexcept to most APIs that are not intended to throw.
Added memory utilities that can read/write to unaligned memory location (ongoing ARM support).
Removed unimplemented instruction scheduler, will be added back when it's working.