opr: Convert to using libtool

opr: Convert to using libtool

Convert opr so that it uses libtool. For backwards compatibility we
still build libopr.a, but we do so as a static convenience library.

As libopr.a may, in the future, be converted to an LWP library, change
all of the pthreaded binaries so that they link against the libtool
library liboafs_opr.la

Change-Id: Icee04ff4745334f06ffba16df5bb07fc9dcc0b54
Reviewed-on: http://gerrit.openafs.org/8034
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>