Bug 1007878 part 1.  Add parsing of MozMap to the WebIDL parser.  r=khuey
Bug 1007878 part 2.  Add a C++ type to represent MozMap.  r=khuey
Bug 1007878 part 3.  Add JS-to-C++ conversion for MozMap.  r=khuey
Bug 1007878 part 4.  Add C++-to-JS conversion for MozMap.  r=khuey
Bug 1007878 part 5.  Implement callback codegen for MozMap.  r=khuey