Recent modifications to the Python script interpreter caused some problems

when handling one-liner commands that contain escaped characters.  In
order to deal with the new namespace/dictionary stuff, the command was
being embedded within a second string, which messed up the escaping.

This fixes the problem by handling one-liners in a different manner, so they
no longer need to be embedded within another string, and can still be
processed in the proper namespace/dictionary context.

llvm-svn: 123467