minor, switch to ax_lib_ev.m4 for libev detection

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>

Conflicts:
	configure.ac
minor, call AC_CHECK_HEADER([ev.h]) solely for the side-effect of defining HAVE_EV_H

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'bld/dist' into next

* bld/dist:
  minor, call AC_CHECK_HEADER([ev.h]) solely for the side-effect of defining HAVE_EV_H
  minor, switch to ax_lib_ev.m4 for libev detection
Merge branch 'next'

* next:
  minor, call AC_CHECK_HEADER([ev.h]) solely for the side-effect of defining HAVE_EV_H
  minor, switch to ax_lib_ev.m4 for libev detection
  fix, don't check for CXX compiler
  hygiene, rename global graph object in xross-quo (to avoid shadows)
  hack, work around clang bug in xross-quo
  Revert "chore, allow clang to fail (bug in clang triggered)"
  chore, allow clang to fail (bug in clang triggered)
  minor, override unser{mod,inc}dir taken from unserding's pc file