refactor: module -> module_ with typedef (#2544)

* WIP: module -> module_ without typedef

* refactor: allow py::module to work again
diff --git a/docs/advanced/pycpp/object.rst b/docs/advanced/pycpp/object.rst
index 70e493a..6c7525c 100644
--- a/docs/advanced/pycpp/object.rst
+++ b/docs/advanced/pycpp/object.rst
@@ -56,12 +56,12 @@
 .. code-block:: cpp
 
     // Equivalent to "from decimal import Decimal"
-    py::object Decimal = py::module::import("decimal").attr("Decimal");
+    py::object Decimal = py::module_::import("decimal").attr("Decimal");
 
 .. code-block:: cpp
 
     // Try to import scipy
-    py::object scipy = py::module::import("scipy");
+    py::object scipy = py::module_::import("scipy");
     return scipy.attr("__version__");
 
 
@@ -81,7 +81,7 @@
 .. code-block:: cpp
 
     // Use Python to make our directories
-    py::object os = py::module::import("os");
+    py::object os = py::module_::import("os");
     py::object makedirs = os.attr("makedirs");
     makedirs("/tmp/path/to/somewhere");
 
@@ -196,9 +196,9 @@
     #include <pybind11/numpy.h>
     using namespace pybind11::literals;
 
-    py::module os = py::module::import("os");
-    py::module path = py::module::import("os.path");  // like 'import os.path as path'
-    py::module np = py::module::import("numpy");  // like 'import numpy as np'
+    py::module_ os = py::module_::import("os");
+    py::module_ path = py::module_::import("os.path");  // like 'import os.path as path'
+    py::module_ np = py::module_::import("numpy");  // like 'import numpy as np'
 
     py::str curdir_abs = path.attr("abspath")(path.attr("curdir"));
     py::print(py::str("Current directory: ") + curdir_abs);