GALAHAD 4.2.0

This release includes the new package clls for linearly-constrained regularized linear least-squares.
It also reflects changes to sifdecode and CUTEst that provide separate names for single-precision function evaluations, so that both single and double versions can co-exist. There have also been a large number of typo corrections in documentation and code comments. It is setting the way for the forthcoming meson build system thate will shortly be replacing make.