QNX: Fix QDir::entryInfoList()

If D_FLAG_FILTER is set, duplicate name entries are filtered out, so
this flag has to be set along with D_FLAG_STAT in the call to dircntl.

Also releaved dependencies between defines__EXT_QNX__READDIR_R,
__EXT_QNX__READDIR64_R and _POSIX_THREAD_SAFE_FUNCTIONS

Back-ported from qtbase: aee59f06e0017e225363d4207d3d96c2b30698e1

Change-Id: Ifa2148cc49544076fcfe8fb88e2a0dfe2404959e
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>