Implemented a new ConvertTextToUTF8() which converts some encoding to UTF8
docview: refactored text encoding version

docview now uses a single fpGUI call to do encoding conversions. This
make is much easier to maintaing - a single method needs to be
modified if new encoding conversions get added.
docview: When searching, do a text encoding conversion of dictionary words.

We forgot to do this before, so sometimes text could not be found.


Also added a note on how we could improve the speed.
docview: extended "File Info" output to include font encoding information.
docview: minor code formatting changes
docview: fixes some compiler hints

- unused variables
- added a note on how to fix another compiler hint (range check error)
docview: greatly improve scrolling speed when help topic contains images

We always did StretchDraw() which is rather CPU intensive. Now we check
the image dimensions first, then decide if StretchDraw() is really
needed or not. If not, then do the much faster DrawImage() call.
docview: Saving topics to IPF now save text as UTF-8 encoded text.

Lets promote Unicode (UTF-8) usage as much as possible. It's much easier
than he stacks of other "old style" encodings.
Merge branch 'docview-codepage-fixes' into develop