Skip over the new 'switch' field in xproto/src/xinput.xml so we can
re-generate the x11 dissector again without the script breaking.

Change-Id: I6d24cf098f370f4c1ff191052e2ea67b7875b33a
Reviewed-on: https://code.wireshark.org/review/5878
Reviewed-by: Stephen Fisher <sfisher@sdf.org>