mark all local functions as static

Source/Core/InputCommon/ControllerInterface/ExpressionParser.cpp

@@ -535,7 +535,7 @@ Expression::~Expression()
 	delete node;
 }
 
-ExpressionParseStatus ParseExpressionInner(std::string str, ControlFinder &finder, Expression **expr_out)
+static ExpressionParseStatus ParseExpressionInner(std::string str, ControlFinder &finder, Expression **expr_out)
 {
 	ExpressionParseStatus status;
 	Expression *expr;