https://github.com/bitcoin/bitcoin/commit/074d584a04ee80123001728ad63d4fd7e9adb828
It's a change to allow namecoin to do merged mining using this code and put extra data in the block chain This extra data has nothing to do with bitcoin, but will simply just increase the bitcoin block chain size It will also allow other crypto currencies to put non-bitcoin data in the bitcoin block chain while using this bitcoin code
That is the reason for this change and the fact that they've hidden this reason rather than stating it ... makes it questionable in the least
N.B. see namecoin site for more details and the web site also states incorrectly that it will not be adding data to the bitcoin block chain - even though they have been asked more than a week ago to correct that http://dot-bit.org/Merged_Mining
