minor, update sxe-aux.m4 to include PKG_CHECK_MODULES_HEADERS macro

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, check for uterus using PKG_CHECK_MODULES_HEADERS

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, migrate unsermon to including either uterus/uterus.h or uterus.h

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, migrate umod-example and strat-example to including either uterus/uterus.h or uterus.h

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
fix, PEBKAC, include unistd.h in ud-meta so close() is declared

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
fix, hygiene, do not include logger.h and dccp.h in main unserding.h

Reason is to avoid possible name clashes with other packages.

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

* code/hygiene:
  fix, hygiene, do not include logger.h and dccp.h in main unserding.h
  fix, PEBKAC, include unistd.h in ud-meta so close() is declared
  chore, migrate umod-example and strat-example to including either uterus/uterus.h or uterus.h
  chore, migrate unsermon to including either uterus/uterus.h or uterus.h
  minor, check for uterus using PKG_CHECK_MODULES_HEADERS
  minor, update sxe-aux.m4 to include PKG_CHECK_MODULES_HEADERS macro