Centralize BOOST_NO_STD_WSTRING error reporting in path.cpp, remove code that allowed V3 code to be skipped in V2 only builds, remove BOOST_FILESYSTEM_VERSION defines from test programs.

svn path=/branches/filesystem-v3/libs/filesystem/; revision=77452
Remove namespace filesystem3 hoisting into namespace filesystem

svn path=/branches/filesystem-v3/boost/filesystem/; revision=77453
Choose the set of tests to be run for regression testing

svn path=/branches/filesystem-v3/libs/filesystem/; revision=77474