Python tests: Add a few tests to check parsing and location of comparisons.

python/ql/test/library-tests/exprs/compare/Test.expected

@@ -0,0 +1,12 @@
+| compare.py:2:1 | Compare | a | Lt | b |
+| compare.py:2:1 | Compare | b | Lt | c |
+| compare.py:4:1 | Compare | x | In | y |
+| compare.py:5:1 | Compare | x | NotIn | y |
+| compare.py:6:1 | Compare | x | Is | y |
+| compare.py:7:1 | Compare | x | IsNot | y |
+| compare.py:8:1 | Compare | x | Lt | y |
+| compare.py:9:1 | Compare | x | Gt | y |
+| compare.py:10:1 | Compare | x | GtE | y |
+| compare.py:11:1 | Compare | x | LtE | y |
+| compare.py:12:1 | Compare | x | Eq | y |
+| compare.py:13:1 | Compare | x | NotEq | y |

python/ql/test/library-tests/exprs/compare/Test.ql

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+
+import python
+
+string loc(AstNode f) {
+    exists(Location l |
+        l = f.getLocation() |
+        result = l.getFile().getBaseName() + ":" + l.getStartLine() + ":" + l.getStartColumn()
+    )
+}
+
+from Compare comp, Expr left, Expr right, Cmpop op
+where comp.compares(left, op, right)
+select loc(comp), comp.toString(), left.toString(), op.toString(), right.toString()

python/ql/test/library-tests/exprs/compare/compare.py

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+
+a < b < c
+
+x in y
+x not in y
+x is y
+x is not y
+x < y
+x > y
+x >= y
+x <= y
+x == y
+x != y