Defined two new functions called u() in the compat module for better unicode string support.

The two functions are defined differently for Python2 and Python3.  The Python3 function simply
returns the text unmodified, as all strings are unicode.  The Python2 function converts the str
type to a unicode type.
Restored the Python3 aliased unicode() function accidentally removed in commit r20789.
The new compat.u() function is now being used for all unicode strings.