gitignore: Add basic files
tests: Add in assembler tests
ax211-util: import ax211 utility
as31: fix up warnings on arm

This fixes warnings on ARM, caused by -Wall.

It also removes parser.y which is causing problems due to bison crashing.
makefile: improve dependency graph

Now the ROM won't get built before the assembler.
readme: add readme file
tree: reorganize projects

This commit reorganizes everything into component sub-directories.  The
assembler now lives in src/as31, and the loader lives in src/ax211.
gitignore: add ax211 to list of ignored files
add makefiles, update gitignore to allow src/(ax211|as31)
makefile: Add root makefile