Make Boost.Ref use BOOST_FORCEINLINE for better performance

[Mathias Gaunard]

boost::ref is used a lot to build expression templates or function objects which typically need to be inlined to get decent performance.

Using BOOST_FORCEINLINE ensures that it does get inlined, even when minimal inlining options are used.

It is very important to do this to get acceptable performance in debug for some the of the libraries I work on, like Boost.SIMD or NT².

See the attached patch.

[Mathias Gaunard]

patch to add BOOST_FORCEINLINE to critical boost::ref functions

[Joel Falcou]

(In [86124]) Fix #9169 - Add BOOST_FORCEINLINE on boost::ref for performance issue

[Peter Dimov]

I tend to only close tickets when the fixes are in the release branch in addition to trunk, because this helps me remember to merge.