Issue

When launching Xephyr with multiple screens Xephyr -screen 640x480 -screen 640x480 :1 we observe the following:
- Erratic mouse pointer behaviour where the mouse pointer jumps back to the first screen or gets stuck forever in one screen
- With a single Xephyr screen the mouse pointer is invisible
- Xephyr segfaults with a trace like the following:

(EE) 2: /lib64/libc.so.6 (0x3020a00000+0x32920) [0x3020a32920]
(EE) 3: /usr/lib64/libpixman-1.so.0 (0x302a200000+0x56c72) [0x302a256c72]
(EE) 4: /usr/lib64/libpixman-1.so.0 (0x302a200000+0x7491e) [0x302a27491e]
(EE) 5: /usr/lib64/libpixman-1.so.0 (pixman_fill+0x31) [0x302a20a5a1]
(EE) 6: Xephyr (fbFill+0x3ba) [0x49f9ca]
(EE) 7: Xephyr (fbPolyFillRect+0x1d2) [0x4b8452]
(EE) 8: Xephyr (0x400000+0x154f0f) [0x554f0f]
(EE) 9: Xephyr (miPaintWindow+0x1ba) [0x4c516a]
(EE) 10: Xephyr (miWindowExposures+0xc8) [0x4c56b8]
(EE) 11: Xephyr (miHandleValidateExposures+0x68) [0x4d6a08]
(EE) 12: Xephyr (SetRootClip+0x26f) [0x46209f]
(EE) 13: Xephyr (0x400000+0x95796) [0x495796]
(EE) 14: Xephyr (0x400000+0x7635b) [0x47635b]
(EE) 15: Xephyr (0x400000+0x766b5) [0x4766b5]
(EE) 16: Xephyr (0x400000+0x96b55) [0x496b55]
(EE) 17: Xephyr (BlockHandler+0x4a) [0x4339ca]
(EE) 18: Xephyr (WaitForSomething+0x15c) [0x46290c]
(EE) 19: Xephyr (0x400000+0x2fc92) [0x42fc92]
(EE) 20: Xephyr (0x400000+0x93dfa) [0x493dfa]
(EE) 21: /lib64/libc.so.6 (__libc_start_main+0xfd) [0x3020a1ecdd]
(EE) 22: Xephyr (0x400000+0x1dc09) [0x41dc09]