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/unusedmethodsremove.cxx

@@ -81,7 +81,7 @@ std::string niceName(const CXXMethodDecl* functionDecl)
         + "::" + functionDecl->getNameAsString()
         + "(";
     bool bFirst = true;
-    for (const ParmVarDecl *pParmVarDecl : compat::parameters(*functionDecl)) {
+    for (const ParmVarDecl *pParmVarDecl : functionDecl->parameters()) {
         if (bFirst)
             bFirst = false;
         else