Add a PD-specific debug window to the Developer tools menu

This is something I've wanted to add for awhile, since we have a window
manager class that makes this kind of thing simple!

All debug window settings are forcibly disabled if the global DEBUGMODE
flag is not set.
pdDIB: in debug mode, keep a global count of DIB creation and destruction

Easy place to check for leaks or runaway drawing code
pdLabel: minimize DIB recreation requests as much as possible

Also, add custom ForeColor support.

This new logic prevents the control from recreating its back buffer
unless absolutely necessary.  (What makes it absolutely necessary?  When
the back buffer size and window size are mismatched, typically due to a
caption change and AutoSize being active.)

Also, I've made further reductions to drawing requests, particularly
when automatically resizing the label as part of a caption change while
AutoSize is active.