[BusyBox] change busybox behavior

[Matt Kraai]

Howdy,

Applet choosing has some strange behavior:

$ ln -s busybox fubar
$ ./fubar echo this
this
$ ./busybox echo --install
busybox: /usr/bin/basename: File exists
...
$ 

The attached patch changes the behavior so that (a) it only checks
for the --install option if the applet being run is explicitly
busybox, and (b) it doesn't silently ignore applets that it
doesn't know about.  That is, the new behavior is:

$ ./fubar echo this
fubar: applet not found
$ ./busybox echo --install
--install
$ 

Normally I'd just apply this, but as we are so close to release
I think some form of official approval is necessary.

Matt