manifest: convert PyString* to PyBytes* Python 2.6 introduced PyBytesObject and PyBytes* as aliases for PyStringObject and PyString*. So on Python 2.6+, PyBytes* and PyString* are identical and this patch should be a no-op. On Python 3, PyStringObject is effectively renamed to PyUnicodeObject and PyBytesObject becomes the main type for byte strings. This patch begins the process of mass converting PyString* to PyBytes* so the C extensions use the correct type on Python 3.

merge: update doc of manifestmerge() per 18c2184c27dc p1 was renamed to wctx by 18c2184c27dc.