Window manager: fix rare Show Window bug

Show Window is an absolute garbage piece of work by Microsoft engineers.
A peripheral search of issues with window messages and this function
turns up a huge list of problems, in every coding environment
imaginable.

Basically, the function does not pass any relevant window messages (e.g.
minimize, restore) to other windows.  Instead, it does a hackish z-order
change of the base desktop.  When the mode is deactivated, windows are
never properly invalidated, because they don't receive any show/hide or
max/min or hide/restore messages.  ARRRRGH

Fortunately, PD can circumvent this due to detailed window focus
tracking, but my hell - what an asinine way to implement it.
Localization: additional failsafes against Type Mismatch errors

The new slider control returns floating-point values even for
integer-only boxes.  This means that preset files might store
floating-point values for integer-only functions.

When it comes time to read those values from file, if locale has changed
since the file was created, decimal separator mismatches may cause the
CLng() function to fail.  As such, CLng() requests now wrap PD's
CDblCustom() function, which handles all locales gracefully.