Ignore needless warnings pulled in from Boost

If we compile with Clang, we need to use at least Boost 1.53, but that
particular version contains code which give unused parameter warnings
and is triggered by opm-core (opm-core itself does not notice that).

Disable these warnings for now (unused parameters in opm-core should be
noticed when compiling the test suites for that project), so we can get
a clean list by default when building our own project.
Replace auto_ptr with unique_ptr

The OPM suite now require a C++11 compiler, so we can safely assume
that this feature is available (and there are other uses of C++11 too,
so the requirement is not really any stricter).
Merge pull request #41 from rolk/041_warn

Remove compiler warnings