lineedit: search applets as well as PATH for tab completion

lineedit: search applets as well as PATH for tab completion

In standalone shell mode search the applet table as well as PATH
when tab completing a command.

Use a stupid linear search:  we're also about to read all the
directories on PATH so efficiency isn't a big concern.

function                                             old     new   delta
add_match                                              -      53     +53
complete_cmd_dir_file                                687     724     +37
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(add/remove: 1/0 grow/shrink: 1/0 up/down: 90/0)               Total: 90 bytes

Signed-off-by: Ron Yorston <rmy@frippery.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>