Begin moving "public" headers to include/

The full changelist:
* src/binaryToObject has been split into src/tools/object-writer (the library), and src/tools/binary-to-object.  As well, the header for object-writer is now in include/tools/object-writer/
* src/codegen public headers (assembler.h, compiler.h, lir.h, registers.h) moved to include/
* abort.h gets properly namespaced and moved to include/
* runtime-array.h gets moved to include/
* a group of simple math functions in common.h were split out into include/avian/util/math.h