TF700t: Function Keys (Fn) (1/2)

Enable function keys in asusdec when CTRL, SHIFT or ALT are pressed

Patchset 2: Rebased

Change-Id: Ib811726c04842f606baf0d4835ffe5b70a5e1192
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>