Squashed 'SPMediaKeyTap/' content from commit af678c2

git-subtree-dir: SPMediaKeyTap
git-subtree-split: af678c2610fe7e6558579ff7cfa086ac037b7aa5
add github.com/nevyn/SPMediaKeyTap as a subtree
add SPMediaKeyTap files to Xcode project
Objective C ARC compatibility
add Carbon.framework (and move WebKit to Framworks group)
switch to SPMediaKeyTap