Don't place smilies inside of pre or code tags. Don't skip smilie after a smilie with an 8 in it. Fix regular expression used for smiley translations to work when there is only one registered emoticon.

Props solarissmoke, soulseekah, mdbitz, yonasy. ht to mdbitz for the Unit Tests and a comprehensive patch.
Fixes #16448, #20124, #25303.


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