Fix typo.
Merge pull request #73 from waywardmonkeys/typo-fixes

Fixed typo.
Added credit.
Documentation work.
Replaced all uses of malloc with calloc.
Clarified names of gamma array helper functions.
Removed superflous casts of allocated memory.
Enabled compilation on OS X 10.6 SDK.
Fixed possible X11 screensaver race condition.
Merge remote-tracking branch 'remotes/upstream/master'