add core.sys.linux.sys.mman

- deprecate MAP_ANON in Posix header
- fix a few architecture enums in core.sys.posix.sys.mman
- fix missing posix_madvise in core.sys.posix.sys.mman
- remove non-available posix_madvise for Solaris
use non-deprecated MAP_ANON on linux

- This needs a future fix when more core.sys.<OS>.sys.mman
  headers are ported.