AC_CHECK_HEADERS is not correctly used in evas_check_engine.m4.

AC_CHECK_HEADERS is not correctly used in evas_check_engine.m4.

The behavior of AC_CHECK_HEADERS is a bit strange: If one has
2 header files foo.h and bar.h and foo.h exists while bar.h
does not, then:

1) with

have headers="no"
AC_CHECK_HEADERS([foo.h bar.h], [have_headers="yes"])

the value of have_headers is "yes"

2) with

AC_CHECK_HEADERS([foo.h bar.h], [have_headers="yes"], [have_headers="no"])

the value of have_headers is "no"

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/evas@39479 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33