[patch] Remove -fobjc-default-synthesize-properties

[Rafael Espíndola]

> I see. If driver always passes -fobjc-default-synthesize-properties then our users will be OK.
> But, we still need to use legacy property synthesis for testing purposes. But we can always use cc1 directly.
> LGTM them.

Sorry, it looks like there is a bit of confusion.

the current status is:
* Driver alway passes -fobjc-default-synthesize-properties
* -cc1 defaults to false, but only 3 tests expect the behavior of not
having -fobjc-default-synthesize-properties.
* There is no -fno-objc-default-synthesize-properties, so the only way
to get the off behavior is to run -cc1 directly.

With the patch we get:
* Driver doesn't pass -fobjc-default-synthesize-properties.
* -cc1 always has behavior we currently get by passing
-fobjc-default-synthesize-properties.
* The 3 tests that were not using -fobjc-default-synthesize-properties
are updated (super-class-protocol-conformance.m,
unimplemented-protocol-prop.m, property-category-1.m)
* -fobjc-default-synthesize-properties  is removed from -cc1 too, so
there is no way to turn it off.

Cheers,
Rafael