Stumbled across such redundant visibility re-specifications when looking at the
odd case of cppu_unsatisfied_iquery_msg declared CPPU_DLLPUBLIC in
cppu/source/cppu/cppu_opt.cxx and used in inline code in
include/com/sun/star/uno/Reference.hxx with only a declaration lacking
CPPU_DLLPUBLIC visible, and wondering how that actually works on Windows.

However, this plugin is probably not worth it being run all the time, so
committing it to compilerplugins/clang/store/.

Change-Id: Ibc3c4e7499213de1b419ce7eb85455cb832e1510