Renaming/cleanup

1. apply_if metafunction has been renamed to eval_if.

2. All _backward algorithm counterparts have been renamed to use reverse_ prefix; e.g. fold_backward became reverse_fold.

3. <boost/mpl/aux_/has_xxx.hpp> header has been made public and became <boost/mpl/has_xxx.hpp>; correspondingly, the BOOST_MPL_NO_AUX_HAS_XXX macro was renamed to BOOST_MPL_CFG_NO_HAS_XXX.

4. <boost/mpl/assert_is_same.hpp> header has been replaced by a more general <mpl/assert.hpp>; the new asserts provide a significantly higher-quality diagnostics. See the table below for the new equivalents of the old macros:

   Before	Now
   BOOST_MPL_ASSERT_IS_SAME(t1, t2)	BOOST_MPL_ASSERT(( boost::is_same<t1,t2> ))
   BOOST_MPL_ASSERT_IS_NOT_SAME(t1, t2)	BOOST_MPL_ASSERT_NOT(( boost::is_same<t1,t2> ))

5. All configuration macros has been renamed to include CFG prefix; in particular, BOOST_MPL_NO_FULL_LAMBDA_SUPPORT has become BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT.

6. The following other public headers/components has been renamed or removed as obsolete:

   iterator_tag.hpp (renamed to iterator_tags.hpp)
   project1st.hpp
   project2nd.hpp
   select1st.hpp
   select2nd.hpp