StrictMode: fix docs to actually compile and add a utility method.

Yes, this is a last minute public API change, but I'm already getting
a lot of inquiries about how to use StrictMode on a GB device but
targetting Eclair or Froyo.  I'd like a simple answer involving
reflection, but the current API is too painful to use via reflection.

I imagine this will be a common request, and it's much easier for us
to write a little blog post about trying it out if there's an easy way
to use it with reflection.

Change-Id: I1f21aaac7e61e5e90d1e4facc0c787d8daf089b1