In CMS.h, you should add
right before the class definition, so the compiler can find the 'Table' class.
Also in 'Table.h' add:
multimap<uint32_t, uint32_t> items;
Finally in 'Table.cpp' you write:
std::multimap<uint32_t, uint32_t> items;
You should generally avoid the 'using namespace xxx' commands, but if you want to use it, put it after all #include's.
using namespace std;