Tokenizer: use a def file for keywords

[Vexu]

This should have better performance than StaticStringMap but I haven't tested that yet.

[Vexu]

This should have better performance than StaticStringMap but I haven't tested that yet.

$ hyperfine -i -w 1 -r 15 "def/bin/arocc compiler_rt.c -fsyntax-only -I ../zig/lib/" "master/bin/arocc compiler_rt.c -fsyntax-only -I ../zig/lib/"
Benchmark 1: def/bin/arocc compiler_rt.c -fsyntax-only -I ../zig/lib/
  Time (mean ± σ):     230.2 ms ±   3.7 ms    [User: 217.5 ms, System: 11.8 ms]
  Range (min … max):   225.5 ms … 241.3 ms    15 runs
 
  Warning: Ignoring non-zero exit code.
 
Benchmark 2: master/bin/arocc compiler_rt.c -fsyntax-only -I ../zig/lib/
  Time (mean ± σ):     218.4 ms ±   4.1 ms    [User: 204.9 ms, System: 12.5 ms]
  Range (min … max):   212.7 ms … 229.1 ms    15 runs
 
  Warning: Ignoring non-zero exit code.
 
Summary
  master/bin/arocc compiler_rt.c -fsyntax-only -I ../zig/lib/ ran
    1.05 ± 0.03 times faster than def/bin/arocc compiler_rt.c -fsyntax-only -I ../zig/lib/

I guess not.