htmlios: Set HTML title (backwards incompatible!)

"-t foo" originally only created a <div> containing the title. Now it
creates that <div> and sets <head><title>foo</title></head> when using
the default template.

This is backwards incompatible if you're using custom templates: Replace
your existing "$title" with "$div_title" and, if you like, add
"$head_title" to your <head>.