dix: unexport and move maxBigRequestSize
- this symbol is a server configuration flag (can be passed via cmdline) for limiting the max size of big-requests. there shouldn't be any need to use it outside the core X server (in server modules like drivers or external extension) - therefore unexport it
- in order to reduce namespace pollution of public (server module API) headers, create a new internal header for those tings (more to come)
Signed-off-by: Enrico Weigelt, metux IT consult info@metux.net