minor, provide manual check for libev's headers on distros without libev.pc file

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
fix, PEBKAC, define sxe_cv_feat_expat everywhere

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, execute user provided ACTION_IF_NOT_FOUND in SXE_CHECK_EXPAT

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

* bld/dist:
  chore, execute user provided ACTION_IF_NOT_FOUND in SXE_CHECK_EXPAT
  fix, PEBKAC, define sxe_cv_feat_expat everywhere
  minor, provide manual check for libev's headers on distros without libev.pc file
Merge branch 'next'

* next:
  chore, execute user provided ACTION_IF_NOT_FOUND in SXE_CHECK_EXPAT
  fix, PEBKAC, define sxe_cv_feat_expat everywhere
  minor, provide manual check for libev's headers on distros without libev.pc file