Make readelf not print 'foo@@' for normal symbols

Make readelf not print 'foo@@' for normal symbols

when a symbol 'foo' is exported and non-hidden and hence is
available for resolving from other objects it's unreasonable
for readelf to print it as 'foo@@'.  If it's not available
for unversioned resolving because its version is hidden
(but without name), then continue printing it as 'foo@' to
indicate that something special goes on.