Add configure option to disable remoting.

Disabling remoting includes type proxies, x-domain communication and makes COM unusable.
Hide marshalbyref and contextbound properties under accessors so we can easily configure them out.
Disable most remoting code under DISABLE_REMOTING.

	When remoting is disabled we don't export most of the code needed for it.
	This includes JIT suppport, marshalling support (no remoting related wrappers),
	transparent proxies won't proxy and, finally, ContextBound/MarshalByRef objects
	will no longer be special.
Rework castclass and isinst OPs to ignore transparent proxies under DISABLE_REMOTING.
The runtime no longer need the remoting types under DISABLE_REMOTING.
Merge branch 'mono-disable-remoting'