GCC needs pluggable runtime support for Objective C

We’ve got four runtimes for Objective C now: Apple/NeXT’s, Cocotron’s, the GNU Objective C runtime, and Etoile’s.

Every one requires a modified version of the compiler, meaning three sets of patches to the compiler, plus one included by default. The default runtime is arguably the most limited and antiquated of them all.

Time for a change, folks?

(Anyone want to help write a pluggable backend and simultaneously help me target GObject?)