Fix read-in of a NetCDF dates list

I'm trying to read dates from a NetCDF file. Presumably this worked for some kind of Null-terminated data in some files? For me and simple date strings it didn't and behaved like this minimal example:

char *data = (char*)calloc(length, sizeof(char));
data[0] = 'a'; data[1] = 'b'; data[2] = 'c';
std::string res(&data[1]);

(Giving "bc", or in the case of MeteoIO the first string would be all dates after each other, the next one all dates again but truncated by length strMaxLen, etc.)

Here is how ncdump displays the strings:

dimensions:
        (...)
        DateStrLen = 19 ;
        (...)

data:

 Times =
  "2022-09-18_06:00:00",
  "2022-09-18_07:00:00",
  (...)
  "2022-09-19_02:00:00",
  "2022-09-19_03:00:00" ;

So, is strMaxLen really just an upper limit, and with this fix do we need to take care of string termination before reaching this length afterwards?

assigned to @bavay

approved this merge request

mentioned in commit 966690e1

merged