* Mute icon: Fix minor bugs

- Fix display the mute icon when leaving the audio player
- Disable mute icon in channellist when 'Quickzap in list' active or allow
- Fix hide the mute icon in movie browser, picture viewer,
  file browser and upnp browser
- Font::RenderString(): Use correct value of y for CFrameBuffer::checkFbArea()

src/gui/movieplayer.cpp

@@ -359,6 +359,7 @@ bool CMoviePlayerGui::SelectFile()
 			menu_ret = moviebrowser->getMenuRet();
 	} 
 	else { // filebrowser
+		CAudioMute::getInstance()->enableMuteIcon(false);
 		if (filebrowser->exec(Path_local.c_str()) == true) {
 			Path_local = filebrowser->getCurrentDir();
 			CFile *file;
@@ -394,6 +395,7 @@ bool CMoviePlayerGui::SelectFile()
 			}
 		} else
 			menu_ret = filebrowser->getMenuRet();
+		CAudioMute::getInstance()->enableMuteIcon(true);
 	}
 	if(ret && file_name.empty()) {
 		std::string::size_type pos = full_name.find_last_of('/');