Many PHP strict and code style fix-ups.

I have PHP warnings on, and the current dev of htmltidy complains all over the place.

So I went in and fixed all them up - ensuring that values were set before they were being read etc.
In the process I discovered at least 5 spots where the boring complaint were valid - settings data was genuinely being lost or ignored thank to renaming or typos somewhere in the past. n this case, following up all the trivial PHP STRICT issues did indeed produce better code and identify several real bugs. Sometimes this happens :-)

So here's a reasonably sweeping fix of the stuff that was easy to spot. Just basic code clean-up really, plus a more globally concise way of dealing with 'default' settings.

... plus another 16 code style fix-ups to bring it into line with Drupal standards and the coder.module review.

I see three other outstanding left-over issues, but not sure I want to mess with them tonight.
(the useless use of variable_get('htmltidy_process_input') in htmltidy_nodeapi, the lack of the option to actually save the repaired text (where did that go?!), and the broken-ness of the debugging clause inside htmltidy_string() - that just can't currently work)