suzerain: #3023 add bl_find_edge99

Adds basic implementation of delta99 plus a test case
based on classical Blasius data.  Happily, the implementation
delegates to older B-spline crossing logic.

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@43525 0bd85f0b-c151-43b9-a1e9-27231104551f