iperf: bump to version 2.0.9

iperf: bump to version 2.0.9

iperf2 is a fork of the original unmaintained iperf project, that
continues the development of the iperf 2.x series. Update homepage
link, and download location.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
[Thomas:
 - change the download location to use downloads.sourceforge.net
 - turn the patch into a Git-formatted one, since upstream uses Git as
   its version control system
 - as noticed by Khem Raj, a C99 compiler is needed for the bool type,
   so added AC_PROG_CC_C99 to configure.ac, and consequently added
   IPERF_AUTORECONF = YES.
 - removed two <pkg>_CONF_ENV variables related to the bool type, they
   were added by an older commit
   e13ac0ec8788092c6508636da94fe0198c18dffd back when we had a
   config.cache shared between packages (which is no longer the case
   today)]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>