Python: Add ModuleValue.{isUsedAsModule, isUsedAsScript}

and a few test cases

python/ql/test/library-tests/modules/usage/ModuleUsage.expected

@@ -0,0 +1,5 @@
+| file://:0:0:0:0 | Module builtins | isUsedAsModule |
+| file://:0:0:0:0 | Module sys | isUsedAsModule |
+| imported.py:0:0:0:0 | Module imported | isUsedAsModule |
+| main.py:0:0:0:0 | Module main | isUsedAsScript |
+| mybin:0:0:0:0 | Script script | isUsedAsScript |

python/ql/test/library-tests/modules/usage/ModuleUsage.ql

@@ -0,0 +1,12 @@
+import python
+
+from ModuleValue mv, string usage
+where
+    mv.isUsedAsModule() and usage = "isUsedAsModule"
+    or
+    mv.isUsedAsScript() and usage = "isUsedAsScript"
+    or
+    not mv.isUsedAsModule() and
+    not mv.isUsedAsScript() and
+    usage = "<UNKNOWN>"
+select mv, usage

python/ql/test/library-tests/modules/usage/imported.py

@@ -0,0 +1,6 @@
+def func():
+    pass
+
+if __name__ == "__main__":
+    print("I could have done something interesting...")
+    print("but I didn't")

python/ql/test/library-tests/modules/usage/main.py

@@ -0,0 +1,5 @@
+import imported
+
+if __name__ == "__main__":
+    imported.func()
+    print('Done')

python/ql/test/library-tests/modules/usage/options

@@ -0,0 +1 @@
+semmle-extractor-options: -F script

python/ql/test/library-tests/modules/usage/script

@@ -0,0 +1,3 @@
+#!/usr/bin/env python
+
+print('Under construction :)')