Remove L4 support from main tree.
Haiku Additions.
fileio2-posix: comment
IPRT: -Wunused-parameter.
*: RTFILE becomes a pointer, RTFileOpen++ expands it's flags paramter from uint32_t to uint64_t.
iprt: split out RTFileQueryInfo bits from fileio-posix.cpp into fileio2-posix.cpp to try avoid dragging in getpwuid_r when not needed.