padsp: allow overriding library install location

padsp: allow overriding library install location

The current build script hardcodes the $pkglibdir in the padsp command.
This works and is a reasonable default. However, distributions that
know where they install, can override this path and thus make padsp
work for any architecture that has the library installed by using the
following configure argument:

   --with-pulsedsp-location='/usr/\\$$LIB/pulseaudio'

This works because ld.so considers $LIB a variable that will expand to
several location paths, depending on the architecture of the binary
being executed.

In debian, for example, this would work for libpulsedsp.so installed in
/usr/lib/x86_64-linux-gnu/ for amd64 and /usr/lib/i386-linux-gnu/ for
i386, with a single padsp command.