Problems with multiple definitions.

Having 'helper' be everywhere is trouble, as is terrain, even
though terrain is not everywhere.  Very tempting to dump stuff into
one file, but that's not the right idea.

So, terrain includes some actual memory map information.  This
should be part of main.  But the function (prototypes anyway)
should be available to whatever file needs them, then I can define
them as needed...somewhere else I guess.  Just prototype in hpp,
then define in one file, perhaps terrain.cpp, sigh.

Might have similar issues for helper.hpp, though it worked before.