bldchn, AC_CONFIG_HEADER is obsolete since a long time
ltdl, use LTDLINCL instead of obsolete INCLTDL
ltdl, add make deps on included libltdl
Merge remote-tracking branch 'rudi/bld/cosmetics'

* rudi/bld/cosmetics:
  ltdl, add make deps on included libltdl
  ltdl, use LTDLINCL instead of obsolete INCLTDL
  bldchn, AC_CONFIG_HEADER is obsolete since a long time