fix a packet_list_freeze / thaw pair, if a return comes in it's way

fix a packet_list_freeze / thaw pair, if a return comes in it's way
add a g_warning() call if an error occured while reading from capture file (while doing a live update), usually shouldn't happen but is difficult to debug *if* it happens
add a new log domain LOG_DOMAIN_MAIN and the standard log handler for it
add some (partly commented out) g_log() calls, useful for GUI sequence debugging

svn path=/trunk/; revision=16136