Fix warnings in ExtraTests and Examples

examples/010-TestCase.cpp

@@ -6,7 +6,7 @@
 // And write tests in the same file:
 #include <catch2/catch.hpp>
 
-int Factorial( int number ) {
+static int Factorial( int number ) {
    return number <= 1 ? number : Factorial( number - 1 ) * number;  // fail
 // return number <= 1 ? 1      : Factorial( number - 1 ) * number;  // pass
 }