[gnugo-devel] include file re-org

[Trevor Morris]

http:/www.public32.com/games/go/trevor_1_27.3
 - organize include file order to facilitate pre-compiled headers.
 - use location_to_string in replay_node()
 - improve assertion in sgftreeAddComment()

By adding "gnugo.h" to the top of all (er, many) of the .c files,
the VC compiler can create a pre-compiled header that hugely
increases compile speeds.

-Trevor