Issue #13959: Rename imp to _imp and add Lib/imp.py and begin
rewriting functionality in pure Python.

To start, imp.new_module() has been rewritten in pure Python, put into
importlib (privately) and then publicly exposed in imp.
diff --git a/PC/os2vacpp/config.c b/PC/os2vacpp/config.c
index bbdf6f3..065343e 100644
--- a/PC/os2vacpp/config.c
+++ b/PC/os2vacpp/config.c
@@ -88,7 +88,7 @@
         {"marshal", PyMarshal_Init},
 
         /* This lives it with import.c */
-        {"imp", initimp},
+        {"_imp", initimp},
 
         /* These entries are here for sys.builtin_module_names */
         {"__main__", NULL},