BUG #14279. Fix random glyphs on Windows.

BUG #14279 was encountered because the code that used rand() didn't not
take into consideration that the int value returned by rand() may be
less than the number of point ids in the dataset. On Windows, is was
indeed limited to 32767 (on unixes, it wasn't that low). Thus resulted
in the rand point ids selected being limited to that range.
Fixed that.

Change-Id: Ifd0e13cdba8404776a2388e2c5c3f68c6889a8ca
Merge topic '14279_fix_rand_on_windows_attempt_2' into next

069f1024 BUG #14279. Fix random glyphs on Windows.