From the GCC manual:

`const'
     Many functions do not examine any values except their arguments,
     and have no effects except the return value.  Basically this is
     just slightly more strict class than the `pure' attribute below,
     since function is not allowed to read global memory.

But _get_type() functions obviously *do* read global memory, so it's wrong for us to annotate them as const.  What we really mean is "pure":

`pure'
     Many functions have no effects except the return value and their
     return value depends only on the parameters and/or global
     variables.  Such a function can be subject to common subexpression
     elimination and loop optimization just as an arithmetic operator
     would be.