A (possibly contentious?) change in the public headers. Those names were never
part of any specification, and I don't know why the struct names differed from
the actual type name. But with C++, which takes the original struct declaration
as the original name, it was affecting the type's internal symbols.
This shouldn't affect user code since ALCdevice_struct and ALCcontext_struct
were never part of the spec. If issues arise from this change, it should be
reported.
Protected visibility is like default visibility, in that functions will be
"exported" from the library. However, it also guarantees that references to the
functions from within the library will be to the library's version, even if the
symbols are overriden by the application.
