XSetModifierMapping: Use Data instead of GetReqExtra

Handle arbitrary length data in the same fashion as other calls,
avoiding need to ensure it fits all in the request buffer.

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Refactor common code from XAddHost & XRemoveHost into single function

On the Xlib side, the only real difference is the mode flag we send
to the server with the address, so just make that an argument to the
function with the common code for packing the address into the request.

(Aside from labels, gcc 4.7.2 generates identical code before & after
 this change due to inlining, verified via diff of gcc -S output.)

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
omGeneric: remove space between struct name & member name

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>