Fix compilation with iso C standard (c89, c99 and c11)

- References to the compiler extension `typeof` have been changed to
`__typeof__` for portability. See [GCC's documentation][1] about
`typeof`.

- Added the definition `_POSIX_C_SOURCE` in the source files that are
using functions not defined in by the POSIX standard, fixing a few
occurences of `sigset_t` not being defined.

- Added the definition `_DEFAULT_SOURCE` in `setup.c` and
`syscall.c` for respectively the `madvise` function (`posix_madvise` exists,
but there is not equivalent for`MADV_DONTFORK`), and `syscall`.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Typeof.html

Signed-off-by: Simon Zeni <simon@bl4ckb0ne.ca>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
5 files changed