bug#1267: Emacsclient can't find terminal in daemon mode

[Chong Yidong]

$ emacs --daemon
$ emacsclient foo.m
Waiting for Emacs...

Emacsclient then stops, waiting indefinitely (IIUC, it opens a frame on
the emacs daemon's "fake" terminal, which is inaccessible to the user).
By contrast, `emacsclient -c foo.m' and `emacsclient -t foo.m' do the
right thing.

I think the Emacs server should do the right thing automatically, but
dunno how hard that would that be to implement.