[rfa] Fix remote debugging

[Andrew Cagney]

> Your recent patch made it mandatory for any target which implements
> to_xfer_partial to support TARGET_OBJECT_MEMORY, i.e. its
> to_xfer_memory will be ignored.  remote.c doesn't meet this new
> requirement.  I didn't check all the other targets with _partial
> methods.
> 
> OK?  Tested on i386-pc-linux-gnu using gdbserver.  Brings test results
> from unspeakable back to merely disappointing.

There's no gdbserver.exp unit test, wasn't one going to be added?  (the 
patch is ok)

Andrew