Bump compiler plugins Clang baseline to 5.0.2

...as discussed at
<https://lists.freedesktop.org/archives/libreoffice/2018-November/081435.html>
"minutes of ESC call ..."

Change-Id: Ia053da171d59747984546f38e19da808825b4f79
Reviewed-on: https://gerrit.libreoffice.org/63832
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

compilerplugins/clang/redundantinline.cxx

@@ -137,14 +137,7 @@ private:
     }
 
     bool handleNonExternalLinkage(FunctionDecl const * decl) {
-        if (decl->getLinkageInternal() >=
-#if CLANG_VERSION >= 50000
-            ModuleLinkage
-#else
-            ExternalLinkage
-#endif
-        )
-        {
+        if (decl->getLinkageInternal() >= ModuleLinkage) {
             return false;
         }
         if (!compiler.getSourceManager().isInMainFile(decl->getLocation())) {