capital_P_dangit() breaks case sensitivity within tags

[ozh]

this is Wordpress <img src="/img/Wordpress.png"/>

should become:

this is WordPress <img src="/img/Wordpress.png"/>

capital_P_dangit() should not modify text inside HTML tags. (Somewhere else too maybe?)

Now maybe this is going to be a bit too regexp intensive compared to the relatively futile purpose? :)

#13971