Three broken cross-references to the "qmake_base" class existed
in the variables chapter. The actual class "qmake_base" is
listed as part of the "qmake*" class so there is no tag taking
a user to the exact "qmake_base" class. Changed the tag to
"ref-classes-qmake*".
(From yocto-docs rev: 96c92e7a26afefbce16a723a071fa203d70ce547)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>