reasons:
* length of the struct is a multiple of 4 according to spec.
* list of char may not end at a 4-byte aligned position.
see:
http://cgit.freedesktop.org/xorg/proto/inputproto/tree/specs/XI2proto.txt#n1224
http://cgit.freedesktop.org/xorg/proto/inputproto/tree/XI2proto.h#n454
http://cgit.freedesktop.org/xorg/proto/inputproto/tree/XI2proto.h#n458
(file-positions may become wrong if the spec or header change)
<list type="char" name="name">
<fieldref>name_len</fieldref>
</list>
+ <pad align="4" />
</struct>
<struct name="RemoveMaster">