Add test for the fixed crash with the opt merge of slices.

theano/tensor/tests/test_type_other.py

+""" This file don't test everything. It only test one past crash error."""
+import theano
+from theano.tensor.type_other import MakeSlice, make_slice
+
+
+def test_make_slice_merge():
+    # In the past, this was crahsing during compilation.
+    i = theano.tensor.iscalar()
+    s1 = make_slice(0, i)
+    s2 = make_slice(0, i)
+    f = theano.function([i], [s1, s2])
+    nodes = f.maker.fgraph.nodes
+    assert len([n for n in nodes if isinstance(n.op, MakeSlice)]) == 1
+    theano.printing.debugprint(f)
\ No newline at end of file