Upgrade to SuiteSparse-4.2.0

With SuiteSparse-4.2.0 Tim Davis added a function cholmod_version so
that the version of CHOLMOD could be checked using the contents of the
compiled library (shared object) only.  During transition a similar
function jl_cholmod_version is defined in deps/SuiteSparse_wrapper.c
to be used with earlier versions of SuiteSparse.  The version is
important because a change in the fields in the cholmod_factor struct
between version 2.0.x and version 2.1.0 of CHOLMOD must be reflected
in the c_CholmodFactor type.