[Patch] for Mail_mimeDecode

In the need of a uudecode function, that both extracted and removed uuencoded sections from a string, I made some improvements to the existing uudecode() in Mail_mimeDecode. The patched uudecode() lets the user choose between preserving all uuencoded sections, removing only successfully extracted sections, and removing all uuencoded blockes. Additionaly the user can provide a replacement string, that will replace the removed sections. While at it, I saw that the $_input is actually only used within Mail_mimeDecode(), and that there also is some unnessesary variable duplication, so I also made a second patch, which takes care of this. The patch also makes a minor change in _decode(), where 'text/plain' and 'text/html' had separate but identical code. Heino