Add ability to answer call with hardware HOME button (1/2)

(preparation for winter time)
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<New edits>:
PS2: Fix port forward compatibility issues and fix up double if statement used in 4.1
PS3: Fix brace derp
Change-Id: I88ff168e3bb1accab9a531267812333c0ae68059

Conflicts:

	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java