New method HasMsg() is added in Message_MsgFile class to check if message with given key is registered.
That method is used in Message_Algorithm to check if message is defined on given level of class hierarchy.
Generation of error message in Message_MsgFile::Msg() is revised: now it includes a message key and gets added to the registry, to avoid re-generation in case of multiple requests.
Access to message registry maintained by the Message_MsgFile class is protected from concurrent access by mutex.
License statement text corrected; compiler warnings caused by Bison 2.41 disabled for MSVC; a few other compiler warnings on 54-bit Windows eliminated by appropriate type cast
Wrong license statements corrected in several files.
Copyright and license statements added in XSD and GLSL files.
Copyright year updated in some files.
Obsolete documentation files removed from DrawResources.
