bltSelection

[Casper Boemann]

Hi

I suggest changing bitBlt (and all composite operations) to take an alpha mask 
into consideration)

This is because currently bltSelection is flawed:
 - it's colorspace dependent. It assumes channels are 1 byte
 - it applies the selection to the source.
 - it uses "alpha" as MIN(sel,alpha).
 - it blits 1 pixel at a time

Every composite op needs to be changed though to take a Q_UINT8 *sel pointer 
and if the pointer is !=0 use it

bitBlt would then pass NULL as the pointer
bltSelection would pass a pointer to the selection data.
bltExtSelection would pass a pointer to the external selection data.

-- 
best regards / venlig hilsen
Casper Boemann