Update 'Reserving a memory area inside a program' chapter to current reality.
Some other small changes.
Merge pull request #53 from groessler/gh-pages_to_pull

More Atari documentation updates
rename LOWDATA segment to LOWBSS
Merge pull request #55 from groessler/gh-pages_to_pull

doc update: rename LOWDATA segment to LOWBSS
Rename 'syschk' symbol in the linker config file, which forces inclusion
of the 'system check' load chunki, to '__SYSTEM_CHECK__'.
Merge remote-tracking branch 'upstream/gh-pages' into gh-pages-sgml