message: Ensure sprs_suitesparse_camd compiles with MSRV
diff: @@ -2,6 +2,11 @@ use sprs::errors::SprsError;
  use sprs::{CsStructureI, CsStructureViewI, PermOwnedI, SpIndex};
  use suitesparse_camd_sys::*;
  +// FIXME should be using SuiteSparseInt::MAX but this will not compile
  +// in rust 1.42 as u32::MAX was introduced in 1.43. This can be changed if
  +// the MSRV is bumped.
  +const MAX_INT32: usize = std::u32::MAX as usize;
  +
  /// Find a permutation matrix P which reduces the fill-in of the square
  /// sparse matrix `mat` in Cholesky factorization (ie, the number of nonzeros
  /// of the Cholesky factorization of P A P^T is less than for the Cholesky
  @@ -27,7 +32,7 @@ where
  }
  let mut control = [0.; CAMD_CONTROL];
  let mut info = [0.; CAMD_INFO];
  - let (camd_res, perm) = if n <= SuiteSparseInt::MAX as usize {
  + let (camd_res, perm) = if n <= MAX_INT32 {
  let constraint: *const SuiteSparseInt = std::ptr::null();
  let mat: CsStructureI<SuiteSparseInt, SuiteSparseInt> =
  mat.to_other_types();
  