bug#9051: alternate editor does not allow program with arguments

[Peter Eisentraut]

I set

ALTERNATE_EDITOR='nano -t'

but that fails when it is being invoked:

emacsclient test.c
emacsclient: connect: Connection refused
emacsclient: error executing alternate editor "nano -t"

(Side issue: It might be nice to append strerror() to that error
message.)

The problem is that emacsclient interprets the alternate editor setting
as an executable name rather than a shell command.  This is in contrast
with the usual handling of the EDITOR environment variable, which is not
rarely set to values such as

EDITOR='nano -t'
EDITOR='emacsclient -t'
EDITOR='emacs -nw'

It would be very convenient and useful if the ALTERNATE_EDITOR
environment variable had the same behavior as the EDITOR variable in
that regard.