added Changelog entry for rev 1305/1306

git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@1307 81a1dc3b-b13d-400b-aceb-764788c761c2
ser_posix: added support for faster baudrates than 230400 on posix based systems
butterfly: implemented a variabel timeout for the erase call in the avr109 protocol. Needed to support AVRs with more than 128kB programm memory.