Move the integer type out of 'derived' and into 'primitive'. This permits us

to explain that derived types are all composed of other types, which primitive
types aren't. Without moving integer out of derived, this wouldn't be true.

Perform a few trivial cleanups; 'i1' went from a link to #t_primitive to
#t_integer (a holdover from when it was a bool type I suppose).

llvm-svn: 82884