PBE1.4 update - section 1.7 change heading Class Browser -> System Browser
Just advance notice to veto this since changing a section heading is
more than a minor edit...
The existing PBE1 has section 1.7 heading as "The Class Browser".
Figure 1.3(a) shows "Class Browser" at the top of the World menu, which
in 1.4 is changed to "System Browser"
so I will similarly change the section 1.7 heading to "The System Browser"