Check for different versions of swapctl() in configure.in

Check for different versions of swapctl() in configure.in

The swapctl() function comes in two flavors. Depending on the OS,
it can take two or three arguments with the following prototypes:

swapctl (int cmd, void *arg, int misc);  (BSD version)
or
swapctl (int cmd, void *arg);            (HP-UX or Solaris version)

This patch adds support for detecting the right version of swapctl()
at configure time.

In addition to HAVE_SWAPCTL, HAVE_SWAPCTL_TWO_ARGS and/or
HAVE_SWAPCTL_THREE_ARGS are defined to reflect the result of the
check.

Signed-off-by: Florian Forster <octo@huhu.verplant.org>