Cleanup namespace importing in abg-interned-str.h
    
    	* include/abg-interned-str.h: Inject std::tr1::shared_ptr,
    	std::string and std::ostream inside the abigail namespace.
    	(interned_string::{interned_string, raw, operator==, operator!=,
    	operator<): Adjust.
    	(operator==, operator!=, operator<<, operator+): Adjust.
    
    Signed-off-by: Dodji Seketeli <dodji@redhat.com>