Created an include directory.

All headers that are not specific to a certain library
and that can be used in external projects now go into
the src/include directory. This change has also required
that all headers specified in source files now be changed
to reflect the new header tree.

In this commit, there was other changes made to compile
recent changes on the windows platform. This included
renaming the Terminal object in src/objects/gdi32 to the
Window object.