Merge pull request #2 from catseye/display-correct-cpu-speed

Display correct CPU speed; store total cycles as double (ANSI C).
Update zextest.c

Updated copyright notice.

Original implementation used int64_t. In retrospect, this was a poor choice. Using double to count cycles is ANSI and has more than enough precision to do so.
Update README.txt

Add revision history.
Merge branch 'master' of git://github.com/catseye/z80emu into catseye