My experience until now is, that the error discovery of Eclipse is horribly buggish without any solutions (Tried __GXX_EXPERIMENTAL_CXX0X__, -std=c++0x
On a fresh Eclipse install, triggering one macro and rebuilding the index solved it:
Projects->Properties->Preprocessor Includes Select GNU C++ Select CDT User Setting entries Press Add
and add a preprocessor macro with name __cplusplus and value 201103L.
Finally, rebuild the index. (Project->C/C++ Index->Rebuild)