New testsuite/boards/local-remote-host.exp board, now with editing on

New testsuite/boards/local-remote-host.exp board, now with editing on

This adds a variant of local-remote-host-notty.exp that forces
pseudo-tty allocation, so that readline/editing is enabled.

 $ ssh localhost gdb -q
 (gdb) show editing
 Editing of command lines as they are typed is off.
 (gdb)

vs:

 $ ssh -t localhost gdb -q
 (gdb) show editing
 Editing of command lines as they are typed is on.

We now get, e.g.:

 Running ../../../src/gdb/testsuite/gdb.base/filesym.exp ...
 PASS: gdb.base/filesym.exp: complete on "filesy"
 PASS: gdb.base/filesym.exp: completion list for "filesym"
 PASS: gdb.base/filesym.exp: set breakpoint at filesym

gdb/testsuite/
2014-05-01  Pedro Alves  <palves@redhat.com>

        * boards/local-remote-host.exp: New file.