micro prefix incompatibility with babel

[matt-m-herndon]

The mu prefix returned by babel cannot be interpreted by pint.

import pint
import unicodedata

ureg = pint.UnitRegistry()

# symbol used internally by pint, this works
ureg(unicodedata.lookup('MICRO SIGN'))

# symbol returned by babel, fails
ureg(unicodedata.lookup('GREEK SMALL LETTER MU'))

[hgrecco]

Not sure where babel goes into this. But, there is a definition file that include the prefix and their aliases. Adding this prefix to that file should fix it.