fix '_sysrmdir' for SpartaDOS
Merge pull request #21 from groessler/something_to_pull

fix '_sysrmdir' for SpartaDOS
implement _sysrename for Atari
Don't import tmp1, slipped in by mistake in last commit
fix cleanup of stack
Merge pull request #22 from groessler/something_to_pull

Something to pull
add "tinyshell" test program for file operations
Merge pull request #23 from groessler/something_to_pull

add "tinyshell" test program for file operations