Added dict comprehension tests

Signed-off-by: Vinzenz Feenstra <evilissimo@gmail.com>

test/tests/dictcomp.py

+print {i: j for i in range(4) for j in range(4)}
+
+def f():
+    print {i: j for i in range(4) for j in range(4)}
+    # print i, j
+f()
+
+
+# Combine a list comprehension with a bunch of other control-flow expressions:
+def f(x, y):
+    # TODO make sure to use an 'if' in a comprehension where the if contains control flow
+    print {y if i % 3 else y ** 2 + i: (i if i%2 else i/2) for i in (xrange(4 if x else 5) if y else xrange(3))}
+f(0, 0)
+f(0, 1)
+f(1, 0)
+f(1, 1)
+
+# TODO: test on ifs
+
+def f():
+    print {i : j for (i, j) in sorted({1:2, 3:4, 5:6, 7:8}.items())}
+f()
+
+# The expr should not get evaluated if the if-condition fails:
+def f():
+    def p(i):
+        print i
+        return i ** 2
+    def k(i):
+        print i
+        return i * 4 + i
+
+    print {k(i):p(i) for i in xrange(50) if i % 5 == 0 if i % 3 == 0}
+f()
+
+def f():
+    print {i: j for i in xrange(4) for j in xrange(i)}
+f()
+
+def f():
+    j = 1
+    # The 'if' part of this list comprehension references j;
+    # the first time through it will use the j above, but later times
+    # it may-or-may-not use the j from the inner part of the listcomp.
+    print {i: j for i in xrange(7) if i % 2 != j % 2 for j in xrange(i)}
+    f()
+
+def f():
+    # Checking the order of evaluation of the if conditions:
+
+    def c1(x):
+        print "c1", x
+        return x % 2 == 0
+
+    def c2(x):
+        print "c2", x
+        return x % 3 == 0
+
+    print {i : i for i in xrange(20) if c1(i) if c2(i)}
+f()
+
+def control_flow_in_listcomp():
+    print {(i ** 2 if i > 5 else i ** 2 * -1):(i if i else -1) for i in (xrange(10) if True else []) if (i % 2 == 0 or i % 3 != 0)}
+control_flow_in_listcomp()