ClangCodeModel/TextEditor: Add support for highlighting parameters

This is already built into clang, so we just need to expose it to the
highlighter and the UI.

Fixes: QTCREATORBUG-24880
Change-Id: I6d0595af2589a9b69eb954aafad46457ab2c5752
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/languageclient/semantichighlightsupport.cpp

@@ -80,7 +80,7 @@ static Utils::optional<TextEditor::TextStyle> styleForScopes(const QList<QString
         {"variable.other.member", TextEditor::C_FIELD},
         {"variable.other.field", TextEditor::C_FIELD},
         {"variable.other.field.static", TextEditor::C_GLOBAL},
-        {"variable.parameter", TextEditor::C_LOCAL},
+        {"variable.parameter", TextEditor::C_PARAMETER},
     };
 
     for (QString scope : scopes) {