More constexpr and noexcept support.

Note 1: Forwarding functions are specified as a C++14 constexpr since
std::forward is not a constexpr within C++11.

Note 2: Though I'm not sure why it doesn't compile, some declarations
are specified as a C++14 constexpr or non-constexpr.

Note 3: Boost.Tuple adaptation and TR1-based tuple implementations are
not constexpr.

preprocess/wave.cfg

@@ -8,10 +8,12 @@
 -DBOOST_FUSION_CREATE_PREPROCESSED_FILES
 -D_WIN32
 -D_M_IX86
+-NBOOST_CLANG
 -NBOOST_STATIC_ASSERT
 -NBOOST_FORCEINLINE
 -NBOOST_CONSTEXPR
 -NBOOST_CXX14_CONSTEXPR
+-NBOOST_NOEXCEPT
 -NBOOST_NO_CXX11_RVALUE_REFERENCES
 -NBOOST_MPL_ASSERT
 -NBOOST_MPL_ASSERT_MSG