portable mode enabled in runtime

src/common/portable.c

@@ -0,0 +1,14 @@
+#include  <io.h>
+
+int
+portable_mode ()
+{
+	if ((_access( "portable-mode", 0 )) != -1)
+	{
+		return 1;
+	}
+	else
+	{
+		return 0;
+	}
+}

src/common/portable.h

@@ -0,0 +1 @@
+int portable_mode ();