Fix a small bug in transition_brightness().
Debug build option.

Default is now -O2, with debug info included (and optimizations off)
if DEBUG is non-empty.
Trivial OSX tweaks.

Omit an unused struct member based on EVENTTAP_HOTKEYS.
Add small .gitattributes file.

Just skip .git{ignore,attributes} when creating archives.
Fix missing newlines in a couple elog() calls.