Also define noreturn w/o <stdnoreturn.h> and move it to macro.h instead
of in the testsuite.
Based on similar commit on systemd by Shawn Landden
<shawn@churchofgit.com>.
It's used in so many places without checking, that's really pointless to
check for it in macro.h.
Also remove AC_C_TYPEOF from configure.ac since we don't use -ansi.
Commit 8efede20ef ("Use _Static_assert") introduced the usage of
_Static_assert(). However, _Static_assert() is a fairly new thing,
since it was introduced only in gcc 4.6. In order to support older
compilers, this patch adds a configure.in test that checks whether
_Static_assert() is usable or not, and adjust the behavior of the
assert_cc() macro accordingly.
Only the public header maintains #ifndef in the header, together with
pragma. The other ones contain only pragma.
As reported by Shawn Landden on systemd mailing list this is compatible
with all major compilers and gcc has this since version 3.3.
I hate this kind of READV and WRITEV macros that Gustavo seems to love.
clang-analyzer hates them as well.
I'm not motivated enough to refactor this, but I want a clean clang
report, so just shut it up.
