Add --max-nside option to bayestar_bin_samples

Supports a maximum level of subdivision

(cherry picked from commit dd9b026cac2f69be5bb3106d0c29e41fe8b37d20)
lalinference: mark as version 1.3.1
top-level: mark as version 6.23
Put C on top of AC_LANG stack after MPI check

(cherry picked from commit 8bb0540cdae6f56252c0e48563135514955cbd3b)
SWIG: make wrappings compatible with SWIG v3.0.0

- %typemaps_string_alloc() has an extra argument
- structs containing pointer-to-const members now
  need SWIGLAL(IMMUTABLE_MEMBERS(...))

(cherry picked from commit 4558d05958962d8240e19651c72dc1699fa63807)