Makefile.in: $LOGNAME and $USERNAME not always set

[William Xu <william.xwl@gmail.com>]

There are some lines in Makefile.in running `chown' like this: 

,----
| find $${dest} -exec chown $${LOGNAME:-$$USERNAME} {} ';' ;\
`----

While in macosx, both LOGNAME and USERNAME is unset, thus I got lots of
chown errors while `make install': 

,----
| usage: chown [-fhv] [-R [-H | -L | -P]] owner[:group] file ...
|        chown [-fhv] [-R [-H | -L | -P]] :group file ...
`----

I checked gnu/linux, solaris, they have set $LOGNAME, $USER; macosx has
only set $USER. None of them have set $USERNAME. So it's problematic
here, expecially on macosx. When $LOGNAME is empty, can we fall down to
$USER instead?

-- 
William