Driver: Remove support for -fobjc-gc*

As a first step toward removing Objective-C garbage collection from
Clang, remove support from the driver.  I'm hoping this will flush out
any expected bots/configurations/whatever that might rely on it.

I've left the options behind temporarily in -cc1 to keep tests passing.
I'll kill them off entirely in a follow up when I've had a chance to
update/delete the rest of Clang.

llvm-svn: 288872