TPNGImage help

This version introduces new set of triggers to enable or disable some features.

Trigger name	When the trigger is
	Being used	Disabled
ObjectPascal	SysUtils, Graphics and Classes are used by the unit.	Heavy units are not used but the TPNGObject is not registered as a TGraphic class
ErrorOnUnknownCritical	In case it decoder finds an unknown critical chunk, the application stops.	Unknown critical chunks are ignored by the decoder.
CheckCRC	CRC is checked for all the data readed.	The CRC is not checked (less security for more speed)
RegisterGraphic	Registers TPNGObject as a TGraphic	TPNGObject is not registered as TGraphic
SemiTransparentDraw	Images with partial transparency are draw agains the background	Semi transparency parts are ignored

All this triggers are set in the beginning of pngimage.pas unit. To set them, add (to use) or remove the lines {$DEFINE NameOfTheTrigger}.