extmod/modvfs: Add new "vfs" module with mount/umount and Vfs classes.

They have been moved from the "os" module.

Signed-off-by: Damien George <damien@micropython.org>
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 9a1f045..837115a 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -1744,6 +1744,11 @@
 #define MICROPY_PY_SSL_FINALISER (MICROPY_ENABLE_FINALISER)
 #endif
 
+// Whether to provide the "vfs" module
+#ifndef MICROPY_PY_VFS
+#define MICROPY_PY_VFS (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EXTRA_FEATURES && MICROPY_VFS)
+#endif
+
 #ifndef MICROPY_PY_WEBSOCKET
 #define MICROPY_PY_WEBSOCKET (0)
 #endif