- time() is used to seed the RNG but since it only has second resolution,
  the same values will be generated if it's called multiple times like
  in the bug report

- BASIC using the global rng would be fine except that BASIC Randomize
  takes an optional parameter to set the seed, which should continue
  to be supported, but should not affect the RNG state for non-BASIC
  users of comphelper::random

(regression from df466d79,
 but the old implementation was even more delightfully absurd,
 where Randomize was essentially srand((sal_uInt16)rand()) ...)

Change-Id: I0f30e509de08f933c02ac77c5d932b20e79586c5