[Freeciv-Dev] (PR#12582) gui-win32 disable alpha blending by default

["James Canete" <use_less@xxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=12582 >

When trying a recent CVS build of gui-win32 on Win98, I found that the
AlphaBlend function didn't work, despite it being available.

This patch disables it by default, enabling the fallback ordered dither
path, and adds a local client option to reactivate it.  It also has a
couple fixes for caching mask bitmaps and only using alpha blending when
necessary.

-James Canete

win32-disablealpha.diff
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