Fixed SWIG go for cases when SWIG %import-s another package which is located in a subdirectory.

Examples/test-suite/go/go_subdir_import_runme.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"go_subdir_import_a"
+	"testdir/go_subdir_import/go_subdir_import_b"
+	"testdir/go_subdir_import/go_subdir_import_c"
+)
+
+func main() {
+	b := go_subdir_import_b.NewObjB();
+	c := go_subdir_import_c.NewObjC();
+	v := go_subdir_import_a.AddFive(b, c)
+	if v != 50 {
+		panic(0)
+	}
+}