CLAP: Host Posix FD Support

[mfisher31]

      // clap_host_posix_fd_support
      virtual bool implementsPosixFdSupport() const noexcept { return false; }
      virtual bool posixFdSupportRegisterFd(int fd, clap_posix_fd_flags_t flags) noexcept { return false; }
      virtual bool posixFdSupportModifyFd(int fd, clap_posix_fd_flags_t flags) noexcept { return false; }
      virtual bool posixFdSupportUnregisterFd(int fd) noexcept { return false; }