* posix_other: Haiku now has spawn.h
This is added per https://dev.haiku-os.org/ticket/13446
* posix_other: Add Haiku specific Dirent members
* cpuinfo: Add an implementation for Haiku
* distros: Add basic Haiku support
* encodings: update Haiku support
* fenv, math: Haiku now provides libm
* times: Add Haiku struct members
* ansi_c, osalloc: Add Haiku constants
* threads: Add Haiku support
* testament: Haiku uses LIBRARY_PATH
* nim.cfg: Update Haiku support
libnetwork should only be linked if network functions are used
* threads: Haiku does not support -pthread switch
* tworkingdir: Haiku's env is in /bin
* posix_other: add SIGKILLTHR for Haiku
* sockets: link with libnetwork on Haiku
* coro: correct ucontext.h location
http://pubs.opengroup.org/onlinepubs/009696699/basedefs/ucontext.h.html
* coro: ucontext backend is not available on Haiku
Haiku doesn't provide the <ucontext.h> header, as it was removed from POSIX
* coro: fix setjmp backend
The compiler does not allow statements after a noreturn function
* nativesockets: Haiku doesn't support AI_V4MAPPED
* system: hostOS can contains "haiku"
* os: add support for Haiku's packagefs
packagefs is read-only, but there are writable holes to the underlying
file system as well
* os: update constant for Haiku
