Merge branch 'next'

* next:
  chore, fix, actually descend into libltdl
  chore, put at least half the ugly bits to ltdl initialisation into SXE_CHECK_LIBLTDL
  ltdl, workaround libtool LT_CONFIG_H bug
  ltdl, use LTDL_INIT's "recursive" mode
  ltdl, move SXE_CHECK_LIBLTDL to configure.ac
  ltdl, remove unsusd check for ltdl.h
  chore, follow Rudi's uterus changes: use LTDLINCL instead of INCLTDL and add LTDLDEPS
  bldchn, AC_CONFIG_HEADER is obsolete since a long time
  minor, emit state in __wday_{before,after}() builders if set
  chore, adapt proof-of-concept dso xmas2 to using a chain of wday_after() and every() builders
  minor, introduce AFTER_OR_ON and BEFORE_OR_ON wday builders
  minor, make builders streams emit BANG events
  minor, make echs_free_wday() return the stream passed to it in the ctor ...
  fix, PEBKAC, make {MON,TUE,...}_{AFTER,BEFORE}() point to an actual builder