bug 166: issues with functions missing on std namespace

* Ugly fix to get it building on OSX 10.6
* Depending on the version of OSX SDK some funcions are not available on
  either the libstdc++ or libc++. Example: round, trunc, acosh, asinh, erf, efc.
  Such functions are not in the std namespace on < 10.6 (default to libstdc++).
  On >= 10.7 libc++ is default and such funcions are on std namespace
* Depending on the toolchain and version of std lib, funcions may or not be on
  the std namespace and on the global namespace. We should test whatever funcion
  we use.
* is complex_missing_std.h really needed?