Added textbox showing RGBA values.
Added padding to pixel values.
improved camera handling while zoomed.
fixed bug in text preprocessor.

symbol definitions guarded by an #ifdef with a false condition were processed (and the symbols were defined) instead of being ignored.
define the __linux__ symbol when preprocessing stylesheet files on Linux.
removed hardcoded styles.
Merge pull request #378 from crest01/new_branch

improved camera handling while zoomed.
cosmetics and minor code tweaks.
Merge branch 'master' of git://github.com/appleseedhq/appleseed
Set RGB text font from stylesheets/default.qss