Actually calculate the mean temperature and salinity reported by
MOM_state_stats().  Due to an oversight, these means were always being reported
as 0.  This changes the output when the debugging flag DEBUG_CONSERVATION=True.
All answers are bitwise identical.

  Added the new function global_mass_int_EFP(), which is analogous to
global_mass_integral but returns its result in extended fixed point (EFP_type)
format and always uses reproducing sums, to facilitate layout-invariant
global integrals but with the potential for deferred global reductions so that
this last step can be combined for various global reductions for efficiency.
All answers are bitwise identical, but there is a new public interface.

  Use global_mass_integral for the debugging diagnostics of the tracer amounts
before and after diffusion in lateral_boundary_diffusion, and replaced a call to
write(*,*) with a call to MOM_mesg to actually write the message.  The
global_mass_integral uses reproducing sums, and is invariant to layout, while
MOM_mesg is preferable for output because it will allow us to more cleanly
control how output is handled and which processors do the writing.  All
solutions are bitwise identical, although some debugging output will change.

  Use reproducing sums for tabulating tracer stocks, and move the global sum for
the tracer stocks form write_energy into call_tracer_stocks.  This involves
changes to the type of an argument (from real to EFP_type) for two arguments to
the internal routine store_stocks.  Existing tracer stock packages will still
work, but to benefit from the reproducing sums, they will also have to change
their reported values from real to EFP_type.  This is demonstrated for two
packages (advection_test_tracer and ideal_age_example), where the stocks are now
found with calls to global_mass_int_EFP(), replacing the previous explicit
sums.  With this change, the reported stock values from these packages are
identical for different PE layouts and can be much more accurate than before,
but they are different from the previously reported values at roundoff (for
positive-definite tracers), but it could be larger for tracers with a near-zero
mean value.  All solutions are bitwise identical, but output changes.

  Modified the remaining tracer packages to use the reproducing stocks.  The
reported stock values from these packages will have changed slightly, but they
now reproduce across PE layouts.  All solutions are bitwise identical, but
output changes.

  Removed trailing white space on two lines.  All answers are bitwise identical.