Use the right libs path for cudnn on mac and don't remove it in nvcc_compiler

theano/configdefaults.py

@@ -338,7 +338,7 @@ AddConfigVar('dnn.include_path',
 
 AddConfigVar('dnn.library_path',
              "Location of the cudnn header (defaults to the cuda root)",
-             StrParam(default_dnn_path('lib64')))
+             StrParam(default_dnn_path('lib' if sys.platform == 'darwin' else 'lib64')))
 
 AddConfigVar('dnn.enabled',
              "'auto', use CuDNN if available, but silently fall back"

theano/sandbox/cuda/nvcc_compiler.py

@@ -224,12 +224,13 @@ class NVCC_compiler(Compiler):
 
         lib_dirs = lib_dirs + std_lib_dirs()
 
-        # config.dnn.include_path add this by default for cudnn in the
-        # new back-end. This should not be used in this back-end. So
-        # just remove them.
-        lib_dirs = [ld for ld in lib_dirs if
-                    not(ld == os.path.join(cuda_root, 'lib') or
-                        ld == os.path.join(cuda_root, 'lib64'))]
+        if sys.platform != 'darwin':
+            # config.dnn.include_path add this by default for cudnn in the
+            # new back-end. This should not be used in this back-end. So
+            # just remove them.
+            lib_dirs = [ld for ld in lib_dirs if
+                        not(ld == os.path.join(cuda_root, 'lib') or
+                            ld == os.path.join(cuda_root, 'lib64'))]
 
         if sys.platform != 'darwin':
             # sometimes, the linker cannot find -lpython so we need to tell it