ExifTool: minor changes to JPEG size tags

This brings us more into line with spec
pdComboBox: fix Unicode text rendering

You live, you learn... :/

Allowing the system to manage Unicode string storage does not actually
work with API combo boxes created inside VB.  The old problem of "VB's
master ANSI pump ruins everything" strikes again; basically, Windows
detects that the master pump for our program is ANSI, so it attempts to
be helpful by down-converting our various Unicode requests to ANSI, even
though the combo box itself is the W variety.

My new solution is to take advantage of the fact that we are
owner-drawn, and simply store (and render) all Unicode strings
ourselves.  It's a bit counterintuitive, but I *also* allow the system
to manage its own string copies for the combo box (copies that I do not
use).  This is important for accessibility technology, because combo
boxes need special handling, owing to their uniqueness of not displaying
their full contents on-screen; accessibility tech will only have access
to ANSI versions of our strings, but this is a compromise I can live
with.

Anyway, it's a bit of a mess, as usual, but the end result is a fully
Unicode-compatible combo box.  This new approach will also prove helpful
for future non-string-based combo boxes (for example, a drop-down for
line styles that consists of only images), because it doesn't rely on
system-managed strings for proper operation.