ClangTools: Make sure URL for clang-tidy checks is always correct

Fixes: QTCREATORBUG-25902
Change-Id: Ifadb6c90cf9a86fc4efb734d6105217b70f9419d
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangtools/clangtoolsutils.h

@@ -42,6 +42,8 @@ namespace Debugger { class DiagnosticLocation; }
 namespace ClangTools {
 namespace Internal {
 
+QString clangTidyDocUrl(const QString &check);
+
 class Diagnostic;
 
 enum class FixitStatus {