Cycles: Remove workaround for MSVC2010 and Boost

We've upgraded to Boost-1.60 and MSVC2013 since the workaround
was originally committed. After checks with current compiler and
libraries the original bug is no longer happening.

This will make string comparison much faster in Windows, solving
synchronization bottlenecks of fewzillion objects.

Thanks Martin Felke (aka scorpion81) for the tests!

intern/cycles/util/util_path.cpp

@@ -66,11 +66,6 @@ void path_init(const string& path, const string& user_path)
 {
 	cached_path = path;
 	cached_user_path = user_path;
-
-#ifdef _MSC_VER
-	// fix for https://svn.boost.org/trac/boost/ticket/6320
-	boost::filesystem::path::imbue( std::locale( "" ) );
-#endif
 }
 
 string path_get(const string& sub)