simgear::ResourceProxy has been renamed to
simgear::EmbeddedResourceProxy in SimGear commit
2200fad30ebfd68cefd461d5443b8612621b4643[1]. Adapt
Docs/README.embedded-resources accordingly.
[1] This was done in order to avoid confusion with the unrelated classes
simgear::ResourceProvider and simgear::ResourceManager.
This document (Docs/README.embedded-resources) explains how to use the
embedded resources system and presents SimGear's CharArrayStream and
ZlibStream families of classes, as well as the ResourceProxy class.