Fixed typos in tutorial doc

doc/tutorial/using_gpu.txt

@@ -152,7 +152,7 @@ The output from this program is
 .. code-block:: text
 
     Using gpu device 0: GeForce GTX 285
-    Looping 100 times took 0.185714006424 seconds
+    Looping 1000 times took 0.185714006424 seconds
     Result is <CudaNdarray object at 0x3e9e970>
     Numpy result is [ 1.23178029  1.61879349  1.52278066 ...,  2.20771813  2.29967761 1.62323296]
 
@@ -208,7 +208,7 @@ the CPU implementation!
 .. code-block:: text
 
     Using gpu device 0: GeForce GTX 285
-    Looping 100 times took 0.0497219562531 seconds
+    Looping 1000 times took 0.0497219562531 seconds
     Result is <CudaNdarray object at 0x31eeaf0>
     Numpy result is [ 1.23178029  1.61879349  1.52278066 ...,  2.20771813  2.29967761 1.62323296]
 
@@ -280,4 +280,4 @@ Changing the value of shared variables
 
 To change the value of a shared variable, e.g. to provide new data to process,
 use ``shared_variable.set_value(new_value)``. For a lot more detail about this,
-see :ref:`aliasing`.
+see :ref:`aliasing`.
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