Avoid bogus loplugin:dllmacro "unnecessary *DLLPUBLIC declaration ..."

...about the definition of __cxxabiv1::__cxa_exception in
bridges/source/cpp_uno/gcc3_linux_x86-64/share.hxx, when a declaration of that
struct has already been seen in /usr/include/c++/7/cxxabi.h in a

  #pragma GCC visibility push(default)
  ...
  #pragma GCC visibility pop

block (so that decl->getAttr<VisibilityAttr>() would point at the first of those
two pragmas).

Change-Id: I4af56be8ce84ace57a809a09da5c44d86fc4237a

compilerplugins/clang/dllmacro.cxx

@@ -76,7 +76,8 @@ bool DllMacro::VisitNamedDecl(NamedDecl const * decl) {
                 << p->getSourceRange();
         }
     }
-    else if (a->getVisibility() == VisibilityAttr::Default) {
+    else if (a->getVisibility() == VisibilityAttr::Default && !a->isInherited())
+    {
         auto p = dyn_cast<CXXRecordDecl>(decl);
         if (p && p->isCompleteDefinition() && !p->getDescribedClassTemplate()) {
             // don't know what these macros mean, leave them alone