Allow 'make install DESTDIR=/path'. This allows packagers to install

into a directory different from the one that was configured.  This
also mirrors the root= feature from 1.3.  We cannot use prefix=,
because both APR and APR-util resolve their installation paths at
configuration time.  This means that there is no variable prefix
to replace.

PR:	7803
Submitted by:	Andreas Hasenack <andreas@netbank.com.br>


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@95686 13f79535-47bb-0310-9956-ffa450edef68