Breaking: #82680 - Removed option to generate PNGs limited to 64 colors 

See forge#82680

Description 

The option to generate PNGs with only 64 colors called $TYPO3_CONF_VARS[GFX][png_truecolor] has been removed.

The public PHP property GraphicalFunctions->png_truecolor has been removed.

Impact 

Setting the option has no effect anymore, as resized PNG images are always truecolor.

Affected Installations 

Any installation having this option disabled.

Migration 

Accessing the Install Tool removes the option. If necessary, the option can be set via TypoScript GIFBUILDER reduceColors.