make doc more clear

doc/library/tensor/nnet/conv.txt

@@ -54,8 +54,9 @@ TODO: Give examples for how to use these things! They are pretty complicated.
       not be call directly as it does not implement a grad function.
       You can enable it by setting THEANO_FLAGS to
       'optimizer_including=conv3d_fft:convgrad3d_fft:convtransp3d_fft'
-      This is not enabled by default because it has some restrictions on
-      input and uses more memory. Also note that it requires CUDA >= 5.0,
+      It does not support strides.
+      This is not enabled by default because it uses more memory.
+      Also note that it requires CUDA >= 5.0,
       scikits.cuda >= 0.5.0 and PyCUDA to run.
       To enable for just one Theano function: