When `GEOSFree` is not available on NT platforms, have to specifically use the MS C library.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12024 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/geos/prototypes/errcheck.py

@@ -1,6 +1,7 @@
 """
  Error checking functions for GEOS ctypes prototype functions.
 """
+import os
 from ctypes import c_void_p, string_at, CDLL
 from django.contrib.gis.geos.error import GEOSException
 from django.contrib.gis.geos.libgeos import lgeos, GEOS_VERSION
@@ -15,8 +16,12 @@ if GEOS_VERSION >= (3, 1, 1):
     free.restype = None
 else:
     # Getting the `free` routine from the C library of the platform.
-    # The C library is obtained by passing None into `CDLL`.
-    libc = CDLL(None)
+    if os.name == 'nt':
+        # On NT, use the MS C library.
+        libc = CDLL('msvcrt')
+    else:
+        # On POSIX platforms C library is obtained by passing None into `CDLL`.
+        libc = CDLL(None)
     free = libc.free
 
 ### ctypes error checking routines ###