Python: Add an extra test for import parsing.

Author: markshannon

python/ql/test/library-tests/ControlFlow/general/Comments.expected

@@ -1 +1,2 @@
 | Module flowtest | 5 |
+| Module imports | 0 |

python/ql/test/library-tests/ControlFlow/general/Lines.expected

@@ -8,3 +8,4 @@
 | Function try_except | 7 |
 | Function try_finally | 7 |
 | Module flowtest | 70 |
+| Module imports | 4 |

python/ql/test/library-tests/ControlFlow/general/imports.py

@@ -0,0 +1,4 @@
+from foo import x, y
+import bar
+from baz import x as a, y as b
+import spam as eggs