Fix compiler warnings, llu lli 64bit (MinGW-w64)

Fix compiler warnings, llu lli 64bit (MinGW-w64)

- time_t is of type 'long long int', when compiled for 64 bit Windows
  (x86_64-w64-mingw32). Use %10llu instead of %10lu in printf and
  %lli instead of %li in dprintf. Requires __USE_MINGW_ANSI_STDIO 1

- Fixes: rrd_lastupdate.c: In function 'rrd_lastupdate':
  rrd_lastupdate.c:76:18:
  warning: format '%lu' expects argument of type 'long unsigned int',
  but argument 2 has type 'time_t {aka long long int}' [-Wformat=]

- Fixes: rrd_graph_helper.c: In function 'parse_shift':
  rrd_graph_helper.c:1458:13:
  warning: format '%li' expects argument of type 'long int',
  but argument 3 has type 'time_t {aka long long int}' [-Wformat=]
  dprintf("SHIFTBY : %li\n",gdp->shval);