deprecate readdir(::Cmd).
pkg2: use readdir instead of run(`ls`) for massive speedup (duh).
pkg2: for now trying to minimize custom types.
pkg2 wip: bug fixes and some refactoring.
add Base.Graphics module. ref #1609

The two basic pieces are geometry and drawing. Drawing is based on a
minimal subset of the Cairo rendering model. I'm not sure whether this
is appropriate; for example we might want instead a stateless
deferred-mode API, or nothing about drawing in Base at all.
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.
a fix to method name reporting with keyword args