Spelling fixes
Fix some obsolete or irrelevant sections
Fixed range for AE.  The point 'y' represents the bar for both opponents
and therefore cannot be cleared because it is shared between both
sides.  TODO: The SGF specification explicitely disallows the AE, AB,
and AW properties to overwrite points resp. stones.  Furthermore, it
explicitely states that the order of properties in a node must not matter.
All that suggests that we should only list points that are really empty
in the AE property so that the "sum" of AE, AB, and AW represents the current
state of the board.  However, we have to investigate first, whether that would
break the reading end of the program.
Remove unused constants
Fix "show cheat" output
Fix "show tutor" output
Silence compiler warnings
Silence compiler warnings
Silence compiler warning
Silence compiler warnings
Fix string continuation bug
Don't dereference pointer in branches where it could be null
Prevent division by zero
Fix external URLs
Fix format strings for unsigned integers
Fix format strings for unsigned integers
Fix format strings for unsigned integers
Fix format strings for unsigned integers
Fix format string for unsigned integers
Fix format string for unsigned integers