update tool chain downloads
|Reported by:||bonefish||Owned by:||mphipps|
We should at least refer to the (strongly) recommended gcc version (http://www.bebits.com/app/ 4011). The ld download can then be removed. Jam doesn't need the two versions 2.4 and 2.5rc3. Just the latter should be fine. Instead a version from the head of our tree should be added (which is a special customized version that allows to be run in subdirectories).