os: Add chdir(), rename().

os/metadata.txt

@@ -1,5 +1,5 @@
 srctype = micropython-lib
 type = package
-version = 0.1.3
+version = 0.1.4
 author = Paul Sokolovsky
 depends = libc

os/os/__init__.py

@@ -13,7 +13,9 @@ except:
 libc = _libc.get()
 
 errno_ = libc.var("i", "errno")
+chdir_ = libc.func("i", "chdir", "s")
 mkdir_ = libc.func("i", "mkdir", "si")
+rename_ = libc.func("i", "rename", "ss")
 unlink_ = libc.func("i", "unlink", "s")
 rmdir_ = libc.func("i", "rmdir", "s")
 getwd_ = libc.func("s", "getwd", "s")
@@ -60,6 +62,10 @@ def mkdir(name, mode=0o777):
     e = mkdir_(name, mode)
     check_error(e)
 
+def rename(old, new):
+    e = rename_(old, new)
+    check_error(e)
+
 def unlink(name):
     e = unlink_(name)
     check_error(e)
@@ -145,6 +151,10 @@ def close(fd):
 def access(path, mode):
     return access_(path, mode) == 0
 
+def chdir(dir):
+    r = chdir_(dir)
+    check_error(r)
+
 def fork():
     r = fork_()
     check_error(r)

os/setup.py

@@ -6,7 +6,7 @@ from setuptools import setup
 
 
 setup(name='micropython-os',
-      version='0.1.3',
+      version='0.1.4',
       description='os module for MicroPython',
       long_description="This is a module reimplemented specifically for MicroPython standard library,\nwith efficient and lean design in mind. Note that this module is likely work\nin progress and likely supports just a subset of CPython's corresponding\nmodule. Please help with the development if you are interested in this\nmodule.",
       url='https://github.com/micropython/micropython/issues/405',