Merge pull request #187 from birth-software/return-0

Add return 0 case

retest/standalone/call_other_file/main.nat

@@ -0,0 +1,6 @@
+import "file.nat";
+
+fn [cc(.c)] main [export]() s32
+{
+    return file.foo();
+}

retest/standalone/first/main.nat

@@ -1,6 +1,4 @@
-import "file.nat";
-
 fn [cc(.c)] main [export]() s32
 {
-    return file.foo();
+    return 0;
 }