Rename macros.
Renamed DISALLOW_COPY_AND_ASSIGN and DISALLOW_IMPLICIT_CONSTRUCTORS to DC_DISALLOW_COPY_AND_ASSIGN and DC_DISALLOW_IMPLICIT_CONSTRUCTORS.
This makes it easier to use this library in projects that have macros with the same name (as is common in Google).
Cherry-picked from c58352dc
Edited by Utkarsh Ayachit