Don't save and restore the zero page locations used.
Saves 19 bytes code (in the exe file) and reduces memory footprint
of the program by 45 bytes (code & bss).
Merge pull request #17 from groessler/something_to_pull

Atari targets: Don't save and restore the zero page locations used.
Remove saving and restoring of zeropage variables.

Merge remote-tracking branch 'upstream/master'

Conflicts:
	cfg/atarixl.cfg
	libsrc/atari/crt0.s