Log Message:
Update to modular-xorg-{server,xephyr}-1.17.4

1.17.4:
Fixes an uninitialized fd_set

1.17.3:
Various bugfixes across the board.  The most visible changes include
fixing GLX extension setup under Xwayland and other non-Xorg servers
(enabling core contexts in more scenarios), and various stability fixes
to glamor and the Present extension.