Normalize the calculated values in createSpaceNormalTangent in
preparation for additional error checks that require the values
to be normalized earlier on.
- createSpaceNormalTangent now normalizes the resulting normal & plane.
- createSpaceNormalTangent_or_fallback has been added that initializes
the matrix even if the tangent or normal aren't usable
(this was previously being done inline).
- createSpaceNormalTangent now returns false if the final tangent
is zero length (this was previously unlikely but possible).
- Remove redundant vector normalize calls.
- Use "r_" prefixed return arguments, order them last.
27cb542393