argument stride in ncmpi_put_vars_all()

[Wei-keng Liao]

According to the NetCDF C interface guide, the argument stride in 
functions nc_get_vars_* and nc_put_vars_* can be NULL, which is 
equivalent to passing (1,1,...,1).

I checked the source file for ncmpi_put_vars_all(), there is no such 
checking and can cause application Segmentation fault if NULL is used. 
This should be easy to correct by using a temp array allocated in 
ncmpi_put_vars_all().

Wei-keng