unix/moduos_vfs: Add missing uos functions from traditional uos module.

Now that the coverage build has fully switched to the VFS sub-system these
functions were no longer available, so add them to the uos_vfs module.

Also, vfs_open is no longer needed, it's available as the built-in open.

ports/unix/modos.c

@@ -126,7 +126,7 @@ STATIC mp_obj_t mod_os_system(mp_obj_t cmd_in) {
 
     return MP_OBJ_NEW_SMALL_INT(r);
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_os_system_obj, mod_os_system);
+MP_DEFINE_CONST_FUN_OBJ_1(mod_os_system_obj, mod_os_system);
 
 STATIC mp_obj_t mod_os_getenv(mp_obj_t var_in) {
     const char *s = getenv(mp_obj_str_get_str(var_in));
@@ -135,7 +135,7 @@ STATIC mp_obj_t mod_os_getenv(mp_obj_t var_in) {
     }
     return mp_obj_new_str(s, strlen(s));
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_os_getenv_obj, mod_os_getenv);
+MP_DEFINE_CONST_FUN_OBJ_1(mod_os_getenv_obj, mod_os_getenv);
 
 STATIC mp_obj_t mod_os_mkdir(mp_obj_t path_in) {
     // TODO: Accept mode param
@@ -207,7 +207,7 @@ STATIC mp_obj_t mod_os_errno(size_t n_args, const mp_obj_t *args) {
     errno = mp_obj_get_int(args[0]);
     return mp_const_none;
 }
-STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_os_errno_obj, 0, 1, mod_os_errno);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_os_errno_obj, 0, 1, mod_os_errno);
 
 STATIC const mp_rom_map_elem_t mp_module_os_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_uos) },

ports/unix/moduos_vfs.c

@@ -33,13 +33,21 @@
 
 #if MICROPY_VFS
 
+// These are defined in modos.c
+MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mod_os_errno_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mod_os_getenv_obj);
+MP_DECLARE_CONST_FUN_OBJ_1(mod_os_system_obj);
+
 STATIC const mp_rom_map_elem_t uos_vfs_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_uos_vfs) },
     { MP_ROM_QSTR(MP_QSTR_sep), MP_ROM_QSTR(MP_QSTR__slash_) },
 
+    { MP_ROM_QSTR(MP_QSTR_errno), MP_ROM_PTR(&mod_os_errno_obj) },
+    { MP_ROM_QSTR(MP_QSTR_getenv), MP_ROM_PTR(&mod_os_getenv_obj) },
+    { MP_ROM_QSTR(MP_QSTR_system), MP_ROM_PTR(&mod_os_system_obj) },
+
     { MP_ROM_QSTR(MP_QSTR_mount), MP_ROM_PTR(&mp_vfs_mount_obj) },
     { MP_ROM_QSTR(MP_QSTR_umount), MP_ROM_PTR(&mp_vfs_umount_obj) },
-    { MP_ROM_QSTR(MP_QSTR_vfs_open), MP_ROM_PTR(&mp_vfs_open_obj) },
 
     { MP_ROM_QSTR(MP_QSTR_chdir), MP_ROM_PTR(&mp_vfs_chdir_obj) },
     { MP_ROM_QSTR(MP_QSTR_getcwd), MP_ROM_PTR(&mp_vfs_getcwd_obj) },
@@ -53,6 +61,10 @@ STATIC const mp_rom_map_elem_t uos_vfs_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_statvfs), MP_ROM_PTR(&mp_vfs_statvfs_obj) },
     { MP_ROM_QSTR(MP_QSTR_unlink), MP_ROM_PTR(&mp_vfs_remove_obj) }, // unlink aliases to remove
 
+    #if MICROPY_PY_OS_DUPTERM
+    { MP_ROM_QSTR(MP_QSTR_dupterm), MP_ROM_PTR(&mp_uos_dupterm_obj) },
+    #endif
+
     #if MICROPY_VFS_POSIX
     { MP_ROM_QSTR(MP_QSTR_VfsPosix), MP_ROM_PTR(&mp_type_vfs_posix) },
     #endif