switched NCMPI write type to MPI_SIGNED_CHAR instead of MPI_BYTE to be compatible with parallel-netcdf 1.7.0

[sluehrs]

Newest parallel-netcdf release (1.7) changed default type to represent NC_BYTE from MPI_BYTE to MPI_SIGNED_CHAR. This has to be reflected in ior to allow NCMPI execution runs.

[wkliao]

Just add a note to this PR.
Starting from 1.7.0, PnetCDF translates internal data types (i.e. data types of the I/O buffer and also used in the API name such as text, schar, uchar, short, int, etc.) to MPI data types based on the table below. MPI_BYTE does no correspond to any internal data type used in NetCDF/PnetCDF APIs.

internal type   example API             MPI datatype
-------------   ----------------------  -----------------
text            ncmpi_put_var_text      MPI_CHAR
schar           ncmpi_put_var_schar     MPI_SIGNED_CHAR
uchar           ncmpi_put_var_uchar     MPI_UNSIGNED_CHAR
short           ncmpi_put_var_short     MPI_SHORT
ushort          ncmpi_put_var_ushort    MPI_UNSIGNED_SHORT
int             ncmpi_put_var_int       MPI_INT
uint            ncmpi_put_var_uint      MPI_UNSIGNED
long            ncmpi_put_var_long      MPI_LONG
float           ncmpi_put_var_float     MPI_FLOAT
double          ncmpi_put_var_double    MPI_DOUBLE
longlong        ncmpi_put_var_longlong  MPI_LONG_LONG_INT
ulonglong       ncmpi_put_var_ulonglong MPI_UNSIGNED_LONG_LONG

[johnbent]

This repo has been ignored for over 4 years. Please contribute instead to the other IOR repo which LANL made when they realized this one had been orphaned:
https://github.com/IOR-LANL/ior
Although it has LANL in the URL, it is actively maintained by a larger community.