Support parameter getGnuConfigureInstallPrefix.

Some GNU tools embed the value of "--prefix" you set to GNU configure. The
famous example is GCC. GCC searches its files from embedded prefix value.

It is provided DESTDIR makefile option in recent versions of GNU autoconf.
(Even if they might have no DESTDIR in ancient versions.) You can install
built binaries where you want to with DESTDIR.

This patch provides parameter named "getGnuConfigureInstallPrefix". The type
is strings. When you specify it, GNU configure is called with "--prefix={your
specidied path}". GNU make is called with "DESTDIR="{install location
specified by NAR plugin}".

The default value is empty. When you don't specify it, NAR plugin works same
as previous versions.