Some code refactoring and cleanup; one small bug fix

Some code refactoring and cleanup; one small bug fix

Some code refactoring, mainly to bring definitions of routines and variables
shared between winboard.c and one of the auxiliary-windows files
whistory.c, wevalgraph.c, wgamelist.c, wengineo.c somewere in a header file
(winboard.h). Unfortunately this made winboard.h dependent on data types
defined in frontend.h, so that the #include order had to be changed in many
other .c files.

The operation revealed one potentially bad bug: engineOutputDialogUp was
written as int in engineo.c, but declared as char in winboard.c.

I also changed the storage mechanism of the the comment and tags window
positions to use WindowPlacement structs rather than simple variables,
so that in the future they can be docked, like the others.

I also removed some remnants of the Analysis window.

The wgamelist.h and wedittags.h header files contained only 3 lines, and
I absorbed them in winboard.h, rather than creating other such nearly empty
headers engineo.h, whistory.h and wevalgraph.h. This affects the make files.