configure: Fix default value for optimize_option, I messed up the test condition

in r86005 and unintentionally changed the default from -O3 to -O2.

 - It's odd the things automated perf testing turns up! :)

 - Also, the configure diff is messed up slightly. It looks like someone either
   didn't regenerate configure correctly (or I didn't), or autoconf has some
   funnyness in it. Eric, any ideas?

This has been at -O2 for so long, that I am slightly nervous that this change
will uncover miscompiles of LLVM on other systems. If that is the case, I think
we should just set the default universally at -O3, and let developers/vendors
use -O3 if they want it and have tested it.

llvm-svn: 100941