Use the new Unicode API

 * Replace PyUnicode_FromUnicode(NULL, 0) by PyUnicode_New(0, 0)
 * Replce PyUnicode_FromUnicode(str, len) by PyUnicode_FromWideChar(str, len)
 * Replace Py_UNICODE by wchar_t
 * posix_putenv() uses PyUnicode_FromFormat() to create the string, instead
   of PyUnicode_FromUnicode() + _snwprintf()
diff --git a/PC/_subprocess.c b/PC/_subprocess.c
index fdcc55b..93e51d3 100644
--- a/PC/_subprocess.c
+++ b/PC/_subprocess.c
@@ -419,14 +419,14 @@
     PyObject* environment;
     wchar_t *wenvironment;
 
-    Py_UNICODE* application_name;
-    Py_UNICODE* command_line;
+    wchar_t* application_name;
+    wchar_t* command_line;
     PyObject* process_attributes; /* ignored */
     PyObject* thread_attributes; /* ignored */
     int inherit_handles;
     int creation_flags;
     PyObject* env_mapping;
-    Py_UNICODE* current_directory;
+    wchar_t* current_directory;
     PyObject* startup_info;
 
     if (! PyArg_ParseTuple(args, "ZZOOiiOZO:CreateProcess",
@@ -454,15 +454,10 @@
     if (PyErr_Occurred())
         return NULL;
 
-    if (env_mapping == Py_None)
-        environment = NULL;
-    else {
+    if (env_mapping != Py_None) {
         environment = getenvironment(env_mapping);
         if (! environment)
             return NULL;
-    }
-
-    if (environment) {
         wenvironment = PyUnicode_AsUnicode(environment);
         if (wenvironment == NULL)
         {
@@ -470,8 +465,10 @@
             return NULL;
         }
     }
-    else
+    else {
+        environment = NULL;
         wenvironment = NULL;
+    }
 
     Py_BEGIN_ALLOW_THREADS
     result = CreateProcessW(application_name,