info: avoid global variable for log_file
info: avoid global variable for log_file

Use user_data to pass the log_file handle to the logger-function.

If one wants to change the log target (e.g. GST_DEBUG_FILE), simply call
gst_debug_remove_log_function() and re-add the handler with the new log-target
using gst_debug_add_log_function ().

mparis/gstreamer,mparis/gstreamer,krichter722/gstreamer,krichter722/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,mparis/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,mparis/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,krichter722/gstreamer,StreamUtils/gstreamer,centricular/gstreamer,krichter722/gstreamer,shelsonjava/gstreamer,mparis/gstreamer