[TYPO3] ts-conf when extending class.tslib_content.php

[PEF]

Hi,

I've made an extension of class.tslib_content.php for the purpose of 
ommitting the border-param from IMG-tags. To control wheater to ommit 
this param or not I've added some code to ext_typoscript_constants.txt 
and _setup.txt and even added som TCA-code to control the feature from 
within the "Text w. image"-element. My intension is to let the code from 
  the content element overrule the code from ext_typoscript_setup.txt.

It works okay except for the fact, that the added params/values in 
setup.txt and TCA aren't available in the extension. Only the 
params/values send to the original class.tslib_content.php are available 
in the extended version.

I can't figure out what goes wrong, but any suggestions are welcome.

Regards
Peter Falk