Fix for running 'python -m' when using swig -builtin

Same as e05b5ea for -builtin.

Also added runtime tests to check 'python -m'.

Examples/python/import_packages/namespace_pkg/split.py

@@ -1,10 +1,20 @@
+import os
+import subprocess
 import sys
+
+print(" Starting subtest " + os.path.basename(__file__))
+
 # Package brave split into two paths.
 # path2/brave/robin.py and path3/brave/_robin.so
 sys.path.insert(0, 'path2')
 sys.path.insert(0, 'path3')
 
 from brave import robin
+print("  Finished from brave import robin")
 
 if not(robin.run() == "AWAY!"):
     raise RuntimeError("test failed")
+
+commandline = sys.executable + " -m brave.robin"
+subprocess.check_call(commandline, shell=True, env = {"PYTHONPATH": "path2:path3"})
+print("  Finished running: " + commandline)