Updated Bridge code to work around struct returns.

1. GetSteamID now returns a straight 64-bit unsigned integer (for now).
Upon further research, the issue appears to reside in returning a struct
(regardless of size) versus returning an integer (even one larger than
a register).
Updated Win32 code for the GetSteamID.

1. Untested!
2. Types now tracks a workaround CSteamID type.
3. GetSteamID now gets a uint64 from the bridge, and wraps it into a
struct for the client.  This is subject to change.