Previously we were inconsistent by generating code for enum definitions
but not generating code for dictionaries. With future changes to the
IDL generator to expose helpers to convert to and from IDL values
this produced circular depdendencies. To solve this problem, also
generate the dictionary definitions in bindings headers.
This implements enough of the Geolocation spec that it is now possible
for websites to retrieve the current geo position or try to watch for
updates (which currently never happen).
As it stands now, it only returns a single emulated position that points
to San Francisco.