according to autoconf people, latest version of autoconf warns of problematic stuff that previous versions did not.
for zabbix, this results in quite a lot of warnings like this :
configure.in:167: warning: AC_LANG_CONFTEST: no AC_LANG_SOURCE call detected in body
some suggestions regarding possible fix (note the backwards compatibility hint) : http://www.mail-archive.com/[email protected]/msg03055.html
full warning output attached