lspclient: declarationProvider is now specified in LSP protocol

See also issue #31

addons/lspclient/lspclientpluginview.cpp

@@ -2254,8 +2254,7 @@ public:
         if (server) {
             const auto &caps = server->capabilities();
             defEnabled = caps.definitionProvider;
-            // FIXME no real official protocol way to detect, so enable anyway
-            declEnabled = caps.declarationProvider || true;
+            declEnabled = caps.declarationProvider;
             refEnabled = caps.referencesProvider;
             implEnabled = caps.implementationProvider;
             hoverEnabled = caps.hoverProvider;

addons/lspclient/lspclientprotocol.h

@@ -76,7 +76,7 @@ struct LSPServerCapabilities {
     LSPCompletionOptions completionProvider;
     LSPSignatureHelpOptions signatureHelpProvider;
     bool definitionProvider = false;
-    // FIXME ? clangd unofficial extension
+    // official extension as of 3.14.0
     bool declarationProvider = false;
     bool referencesProvider = false;
     bool implementationProvider = false;