Merge pull request #2 from dyarnell/master

Adding the ability to set or clear the policy on a principal.
Enable compatiblity with krb5 1.8
Raise exception for init_with_password failures
Merge pull request #4 from Kowh/originkrb1_8

Enable compatiblity with krb5 1.8
Merge pull request #5 from Kowh/originpwerr

Raise exception for init_with_password failures
Merge pull request #3 from dyarnell/master

Distutils enhancements and ifdef checks in error handler initialization.