Allow user install

[Simon J. Gerraty]

On Tue, 26 Jun 2012 11:01:18 -0500, Eric van Gyzen writes:
>INSTALL_OWN is a bit cumbersome.  Its name also doesn't cover other 
>privileged attributes, such as the schg flag.
>
>I like UNPRIVILEGED_INSTALL or USER_INSTALL.  The user can set those to 
>tell the build system what he/she wants.  The build system can then set 
>the other internal variables to make that happen.  Those internal 
>variables can change over time, but the user will still get the right 
>behavior.
>
>The ports system uses INSTALL_AS_USER; the precedent is worth considering.

Thanks - assuming the functionality is wanted, some agreement on the
name of the knob will arise.