Modify _build.py:cython() to be cleaner:

(1) Now uses subprocess.call instead of os.system, so that paths with spaces
    (and the like) are handled properly.

(2) Removes superfluous .c.new files after deciding whether or not to copy
    them to the .c files.

scikits/image/_build.py

@@ -1,6 +1,7 @@
 import os
 import shutil
 import hashlib
+import subprocess
 
 def cython(pyx_files, working_path=''):
     """Use Cython to convert the given files to C.
@@ -26,18 +27,17 @@ def cython(pyx_files, working_path=''):
             # run cython compiler
             cmd = 'cython -o %s %s' % (c_file_new, pyxfile)
             print cmd
-            status = os.system(cmd)
-
+            status = subprocess.call(['cython', '-o', c_file_new, pyxfile])
             # if the resulting file is small, cython compilation failed
             if status != 0 or os.path.getsize(c_file_new) < 100:
                 print "Cython compilation of %s failed. Falling back " \
                       "on pre-generated file." % os.path.basename(pyxfile)
-                continue
-
-            # if the generated .c file differs from the one provided,
-            # use that one instead
-            if not same_cython(c_file_new, c_file):
+            elif not same_cython(c_file_new, c_file):
+                # if the generated .c file differs from the one provided,
+                # use that one instead
                 shutil.copy(c_file_new, c_file)
+            os.remove(c_file_new)
+            
 
 def same_cython(f0, f1):
     '''Compare two Cython generated C-files, based on their md5-sum.
@@ -65,3 +65,4 @@ def same_cython(f0, f1):
     f1.readline()
 
     return md5sum(f0) == md5sum(f1)
+