20190611
  Correct a comment about AMPLFUNC_STROUT in funcadd.h; asldate.c not
changed.

20190605
  New file arith.h1.  On many systems, it may suffice to use arith.h1
as arith.h (by copying or linking arith.h1 to arith.h).
  mach.c, stderr.c:  add simple tests of whether the ASL was compiled
with the right arith.h, assuming IEEE arithmetic.  The tests can pass
with the wrong arith.h without preventing faults if, e.g., Double_Align
needed to be #defined in arith.h.  It is best to "make clean; make"
in the solvers directory after changing compiler options or compilers
for compiling the ASL.  People using cross-compilers must take suitable
care to get arith.h right, ideally using an arith.h derived on the
target system, with the target compiler options and compiler, though
using arith.h1 as arith.h may often work.
