rpcrt4: Errors in sending or receiving packets should result in RPC_S_CALL_FAILED being returned, not RPC_S_PROTOCOL_ERROR.

rpcrt4: Check there is enough space in the buffer and that the size doesn't cause an overflow when copying data to it.

Rename safe_buffer_copy to safe_copy_from_buffer.

OpenGL drivers do not support some low precision internal formats
like GL_RGB5 for fbo color targets. Direct3D application depend on them,
so provide a fallback format for render targets if the requested format
itself is not supported.