Add test for multiline function declaration

Author: facchinm

src/arduino.cc/builder/test/sketch_with_externC_multiline/sketch_with_externC_multiline.ino

@@ -0,0 +1,13 @@
+void setup() {
+  // put your setup code here, to run once:
+  test();
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+
+}
+
+extern "C" {
+	void test() {}
+}

src/arduino.cc/builder/test/try_build_of_problematic_sketch_test.go

@@ -205,6 +205,10 @@ func TestTryBuild039(t *testing.T) {
 	tryBuildWithContext(t, ctx, "sketch12", "sketch12.ino")
 }
 
+func TestTryBuild040(t *testing.T) {
+	tryBuild(t, "sketch_with_externC_multiline", "sketch_with_externC_multiline.ino")
+}
+
 func makeDefaultContext(t *testing.T) *types.Context {
 	DownloadCoresAndToolsAndLibraries(t)