Fix .bss clearing, and call exit() after main()
Replace obsolete moxiedev reference with moxie-cores repo
Merge pull request #2 from atgreen/cleanup

Cleanup
add zero-byte README to shut up automake
make simulator tracing a runtime option (-t)
Kill sim_write_* wrappers, and move sim_read_* to interp.cc
interp: alias 'cpu' at C++ not cpp level
Isolate moxie-specific code and definitions.
sandbox: allocate 64k stack to process
Return exception if non-existent memory accessed. Report sim exceptions.
moxie: fix mmap to not stomp $sp
Remove BSS-clearing and argc/argv load

* BSS clearing was impossible on a read-only memory segment
* argc/argv was incorrect
runtime/crt0: set argc, argv
sandbox: always keep memmap sorted
code movement prior to mmap implementation
implement SYS_mmap (heap allocation)
elf: use ro/rw classes depending on ELF access protection flag
runtime: improve test w/ heap alloc
move machine-class-related code to its own module
moxie: read instructions, dwords in a single memory access