- fix random failures for the "stdlib" and "unistd" tests
- pass the FIXME test

Platform specific:
- FreeBSD:
  * fix build (conflict with /usr/local/include)
  * complete _start(), signal() on amd64
  * check syscall() on amd64
  * reflect the current status in the test suite
- Linux:
  * fork() and pause() may have to be inline (asm/unistd.h)
  * re-introduce ARM OABI
- OpenBSD:
  * complete support for SSP