command: capture command now handles both types commands

command: capture command now handles both types commands

Commands that output progress output and no return value
will have the progress output captured.

Commands that do not output progress output(tcl commands)
will return the tcl return value instead.

The advantage here is that it is no longer necessary to
consider which command one is capturing, it works for
either.

Example #1: capture progress output:

set foo [capture help]

Example #2: capture tcl return value

set foo [capture {set abc def}]

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>