xinput: req ChangeFeedbackControl.mask: add mask

xinput: req ChangeFeedbackControl.mask: add mask

add new enum ChangeFeedbackControlMask to field "mask" as mask

V2: patch revised according to suggestion from Ran Benita:
* changed item name from "ledMode" to "LedMode" ( initial character uppercase )
  to be consistent with the initial uppercase letter of the other items.

V2: added a note to the commit-message
    about multiple items with the same value.

Note:
This enum contains multiple items with the same value.
This is defined that way in the spec.
The reason is probably as follows:
The semantic of those values probably depends on the
the value of field "class_id" of struct "FeedbackCtrl".

spec and code:
http://cgit.freedesktop.org/xorg/lib/libXi/tree/specs/encoding.xml#n1450
http://cgit.freedesktop.org/xorg/proto/inputproto/tree/XI.h#n207
http://cgit.freedesktop.org/xorg/xserver/tree/Xi/chgfctl.c

the following spec just mentions that the field "mask" is a BITMASK,
but does not list its values:
http://cgit.freedesktop.org/xorg/proto/inputproto/tree/specs/XIproto.txt#n1725