gcc 4.8 compatibility issue

Summary

(C++) Communication.cc In file included from /usr/include/c++/4.8/unordered_map:35:0, from Fd_And_Timeout_User.hh:27, from Communication.cc:47: /usr/include/c++/4.8/bits/c++0x_warning.h:32:2: error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support is currently experimental, and must be enabled with the -std=c++11 or -std=gnu++11 compiler options. #error This file requires compiler and library support for the
^ In file included from Communication.cc:47:0: Fd_And_Timeout_User.hh:125:10: error: 'unordered_map' in namespace 'std' does not name a type static std::unordered_map<int,Data> items; ^ Fd_And_Timeout_User.hh: In static member function 'static boolean FdMap::findInItems(int)': Fd_And_Timeout_User.hh:112:12: error: 'items' was not declared in this scope return items.find(fd)!=items.end(); ^

/cc @aknappqwt @mmagyari