Rename [class.member.lookup] to [basic.lookup.class] #8205

The label [class.member.lookup] should be renamed to start with [basic.lookup] because it's part of the specification of name lookup, and its sibling sections are [basic.lookup.general], [basic.lookup.unqual], [basic.lookup.argdep], and [basic.lookup.qual]. The label [basic.lookup.class] seems natural.

Similarly, section [class.qual], which is nested under [basic.lookup.qual], should be renamed to [basic.lookup.qual.class].

This change is proposed to become a part of #7399