qt: remove -fvisibility=hidden CXXFLAG.

Was originally added in 77dc3464c12d262d60fa44d546f5c02cd70a388c for
better supporting KDE and/or Phonon. KDE and Phonon are no longer in
core and apparently Qt will add this automatically if needed now so
this can be removed.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
qt: use upstreamed Mavericks patches.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
qt: update 4.8.5 bottle.

Closes #25105.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>