Add command to make Emacs window fullscreen.

Default keybinding is F11. The command follows freedesktop standards,
so it should work on most desktops, at least in GNU/Linux systems.
Restrict fullscreen feature to X-based systems.

Recent Emacs in OSX already comes with fullscreen support.
Merge pull request #359 from haplo/fullscreen

Add command to make Emacs window fullscreen
Refine fullscreen support
More tips
Remove solarized-theme from the list of default packages
Username fix for windows-nt
Merge pull request #366 from shanmuha/master

Username fix for windows-nt
Adds web-mode and prelude module.
Merge pull request #368 from climatewarrior/add-web-mode

Adds web-mode as prelude module.
Increase ac-delay.
Merge remote-tracking branch 'refs/remotes/upstream/master'