helper: Avoid freeing Comm-held MPI_Comm more than once

Fix ZFP error message.

Ignore files generated by readthedocs.

The `Comm::Free` method may be called more than once by applications.
Although some MPI vendors document that `MPI_Comm_free` sets the
given handle to `MPI_COMM_NULL`, this does not always happen in
practice.  Set the handle to `MPI_COMM_NULL` explicitly to avoid
calling `MPI_Comm_free` more than once for the same handle.

Without this, when compiled with PGI and executed with TAU profiling,
a double-free occurs and causes memory to be corrupted.

Sensible error message when parsing non-bp3

Fix: stringToByteUnits Default

bindings: Factor out MPI-specific Fortran bindings into separate sources

cmake: Fix sst object lib dependency propagation with CMake < 3.14

Co-authored-by: Chuck Atkins <chuck.atkins@kitware.com>

If no unit is appended to, e.g. the `maxbuffersize` string, then
the last two numbers are chopped and things are interpreted as
bytes. For example, 1GByte becomes ~10MByte.

This fixes it and assumes the user meant Bytes.

bp4dbg: rework to use python modules

CMake < 3.14 forget to propagate private dependencies of object
libraries.  Propagate them the same way CMake >= 3.14 do.

added verbose parameter for ssc

Add a Destroyed state to streams

Port CMake python tooling to use upstream FindPython

Move the Fortran `adios2_init` and `adios2_open` generic procedure
implementations for MPI and non-MPI signatures into separate modules.
Compile the MPI-specific sources only when MPI is enabled.

Note that this method of splitting the implementations differs from what
we had before commit b72e908b (bindings: Consolidate MPI and non-MPI
Fortran adios2_init and adios2_open, 2020-02-25).  Previously only one
variant could be built at a time.  Now we can build both and let
applications choose which ones to use (either or both).

Move code conditioned by `ADIOS2_HAVE_MPI_F` into source files that are
built only when that condition is true.  Later this will be useful for
compiling the MPI-specific sources in a separate library.

PGI Fortran 19.10 does not like the VALUE attribute on module procedure
arguments when the procedures are implemented in submodules.  Remove
the attribute to allow that possibility.

Protect SST against EndStep without a successful BeginStep

bindings: Consolidate MPI and non-MPI Fortran adios2_init and adios2_open

Print App ID with timing infa on screen as well as write perf files w…

Combine the `bindings/Fortran/modules/{mpi,nompi}/*` sources to provide
a single definition of the modules providing the `adios2_init` and
`adios2_open` generic procedures.  Include the MPI signatures only when
ADIOS is built with MPI enabled.

Print App ID with timing infa on screen as well as write perf files with app ID, so apps in an MPMD run can be tracked. Fix array values in tasks with no step setting.