More parser work: fixed a few bugs with [[intlinks]] in headers, a bug that caused the paragraph parser to return an empty string, and added a warning/backup-and-restore for when a render stage returns an empty string.
.mceItemFlash, .mceItemShockWave, .mceItemQuickTime, .mceItemWindowsMedia, .mceItemRealMedia {border:1px dotted #cc0000; background-position:center; background-repeat:no-repeat; background-color:#ffffcc;}
.mceItemShockWave {background-image: url(../img/shockwave.gif);}
.mceItemFlash {background-image:url(../img/flash.gif);}
.mceItemQuickTime {background-image:url(../img/quicktime.gif);}
.mceItemWindowsMedia {background-image:url(../img/windowsmedia.gif);}
.mceItemRealMedia {background-image:url(../img/realmedia.gif);}