Fix loading of lumps from directory on OS X

Use POSIX-compliant opendir() / readdir() functions instead fts_open() / fts_read()
Unlike Linux version, on OS X fts_read() inserts extra slash character between source directory and traversed entry paths
Added GetActorPowerupTics ACS function
Merge branch 'master' of https://github.com/Edward850/zdoom
More editing flags

PSX-inspired flags to change the render styles of monsters (and other
things).
Less flags, more generic properties
Updated documentation
CANRAISE state definition

CANRAISE state for allowing a monster to be resurrected without an
infinite frame
Merge branch 'master' of https://github.com/rheit/zdoom
Merge branch 'master' of https://github.com/Edward850/zdoom
Merge branch 'master' of https://github.com/rheit/zdoom
- fixed typo in xlat files (they don't use exactly C syntax.)
Init new non-0 fields for non-UDMF maps.
Hexen too.
Hexen also needs to init 0 fields.
Typo.
Merge branch 'master' of https://github.com/Gaerzi/zdoom
Merge branch 'master' of https://github.com/rheit/zdoom
Merge branch 'master' of https://github.com/coelckers/gzdoom