Add output file option for wayland-tracer

A note about the files imported from Wayland left out in previous
commit:

wayland-os.c, .h, wayland-util.c, .h are imported as is from Wayland
connection.c and wayland-private.h are adapted from Wayland to fit in
here.

All of the above files are from Wayland upstream revision
7ce8eab6b3e9a92bb915391a592a341dc7644fda
Add a missing OPTIONS in help text