Fix error message for invalid parameter overrides (#4559)

src/V3String.h

@@ -130,6 +130,9 @@ public:
     static bool endsWith(const string& str, const string& suffix);
     // Return true if char is valid character in word
     static bool isWordChar(char c) { return isalnum(c) || c == '_'; }
+    // Return proper article (a/an) for a word. May be inaccurate for some special words
+    static string aOrAn(const char* word);
+    static string aOrAn(const string& word) { return aOrAn(word.c_str()); }
 };
 
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