build fix, compile if HAVE_UTERUS_UTERUS_H is undefined

This discovers an odd effect. Seems we will always use
 /usr/include/uterus
even if pkg-config finds
 $HOME/include/uterus

Should be fixed somehow.
Merge remote-tracking branch 'rudi/fixes'

* rudi/fixes:
  build fix, compile if HAVE_UTERUS_UTERUS_H is undefined