javadoc: doesn't generate fields or methods beginning with _ and $ (or Z)

The generated AllNames.html doesn't contain any fields or methods if any of them
begin with _ or $ characters - it can only cope with identifiers that
begin with a-zA-Z, but _ and $ are also valid, as defined in the
language spec. Here's a simple test case, _bug.java:

public class _bug {}

Run "javadoc _bug.java" and look at the AllNames.html file; it won't
list any identifiers. This is on Solaris, JDK 1.1.1 (and 1.1.2), but
as it's the shared code it's applicable to all platforms.