Fix 64-bit time_t in fprintf, printf (MSVC)

Fix 64-bit time_t in fprintf, printf (MSVC)

- In VS2005 and later, the default size for time_t is 64-bit, unless
  _USE_32BIT_TIME_T has been defined to use a 32-bit time_t ...

- Fixes MSVC compiler warnings:
  ./src\rrd_graph_helper.c(1465): warning C4477: 'fprintf' :
  format string '%li' requires an argument of type 'long',
  but variadic argument 1 has type 'time_t'

  ./src\rrd_lastupdate.c(83): warning C4477: 'printf' :
  format string '%10lu' requires an argument of type 'unsigned long',
  but variadic argument 1 has type 'time_t'

  ./src\rrd_tool.c(720): warning C4477: 'printf' : format string '%ld'
  requires an argument of type 'long', but variadic argument 1 has type
  'time_t'
  ./src\rrd_tool.c(724): warning C4477: 'printf' : format string '%ld'
  requires an argument of type 'long', but variadic argument 1 has type
  'time_t'
  ./src\rrd_tool.c(742): warning C4477: 'printf' : format string
  '%10lu' requires an argument of type 'unsigned long', but variadic
  argument 1 has type 'time_t'