Quincey noted the following declarations
are duplicated in netcdf.h and netcdf_par.h
This commit removed the duplicates from netcdf.h
since they are only used when parallism is
enabled.

    /* Use these with nc_var_par_access(). */
    #define NC_INDEPENDENT 0
    #define NC_COLLECTIVE 1

    /* Set parallel access for a variable to independent (the default) or
     * collective. */
    EXTERNL int
    nc_var_par_access(int ncid, int varid, int par_access);