strange tcl dejagnu error

[Michael Chastain]

Oh, shit.  This is mine.

I changed the return type of gdb_file_cmd; and I did a careful job of
changing all the callers in gdb.*/*.exp and lib/*.exp, but since I test
native only, I did not even think about config/*.exp.

The right code is:

  set status [gdb_file_cmd $arg]
  if { [lindex $status 0] != "" } then {
    # gdb_file_cmd failed
    whatever;
  }

See the comment at the front of gdb_file_cmd for the specification
of the return value.

I'll fix this tomorrow.  Sorry!

(And man, is there a lot of funky dead code in config/*.exp).

Michael