config: move STDIO_FUTEXES up a bit

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
test: disable ptytest unless HAS_PTY

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
unistd: allow to turn off getopt_long

The GNU variant of getopt() previously had no way to turn off
getopt_long() support.
stdio: Fix printing 0.0

We were relying on FE_DIVBYZERO being turned off when printing
"%f", +-.0
Avoid the whole issue by looking at the sign-bit (in a rough
approximation).

Note that we do not handle gracefully:
  printf ("\n%llf\n", -0.0);
  printf ("\n%llf\n",  0.0);
nor %Lf for both when NOT cast to long double. Avoiding an FPE due to
broken numbers like these does not make sense to me.

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
test: Some more tests under conditionals

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
mkostemp: fix implementation

mkostemp(char *template, int flags) generates a unique temporary
filename from a template.  The flags parameter accepts three of
the same flags as open(2): O_APPEND, O_CLOEXEC, and O_SYNC.  The
current implementation of mkostemp(3) does not respect the flags
and in fact confuses the flags with the file mode which should
always be S_IRUSR | S_IWUSR.  This patch corrects this issue.

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>