Remove an unused variable
Make internal logging variables static

This avoids polluting the global namespace.
Remove the unnecessary WelsSet/GetLogLevel functions

Nothing actually used the variable that these functions
handled.
Remove an unnecessary local function
Remove some commented out lines
Remove the unnecessary method WelsTraceModuleIsExist(), which always returned true
Don't include a [ENCODER]: prefix in all logging

The same trace module is used for the decoder now as well.
Set a sensible total bitrate when testing multilayer encoding

The previous encoder parameters triggered warning logging in
the encoder.
Merge pull request #942 from mstorsjo/log-cleanup

Clean up some of the logging/trace files
Merge pull request #941 from mstorsjo/test-multilayer-bitrate

Set a sensible total bitrate when testing multilayer encoding