Get rid of deprecated cruft. 

In the very earliest days of OIIO, typedesc.h was one of the first files I wrote, and it was based on a similar concept (though different name) in an open source header that was part of Gelato. I added some #defines for compatibility (at least as much to satisfy my fingers' muscle memory as to help any actual Gelato users who might want OIIO), but whatever the original rationale, there is no reason after all these years to retain these macros. Let's finally excise them.