ltdl, remove bad "recursive" parameter from LT_CONFIG_LTDL_DIR

Actually we were using the default "subproject".
ltdl, correctly use "recursive" mode

This decreases the distdir size about 1.3 MB.
bldchn, AC_CONFIG_HEADER is obsolete since a long time
ltdl, workaround libtool LT_CONFIG_H bug

Building embedded libltdl fails because config.h is located in subdir
src. See libtool bug #12262
http://lists.gnu.org/archive/html/bug-libtool/2012-08/msg00007.html
ltdl, actually use the included libltdl if needed
libtool, remove unused macros
ltdl, use LTDLINCL instead of obsolete INCLTDL
ltdl, add LIBLTDL to LDADD rather than LDFLAGS
ltdl, add make dep to included libltdl
Merge branch 'bld/ltdl'

* bld/ltdl:
  ltdl, add make dep to included libltdl
  ltdl, add LIBLTDL to LDADD rather than LDFLAGS
  ltdl, use LTDLINCL instead of obsolete INCLTDL
  libtool, remove unused macros
  ltdl, actually use the included libltdl if needed
  ltdl, workaround libtool LT_CONFIG_H bug
  bldchn, AC_CONFIG_HEADER is obsolete since a long time
  ltdl, correctly use "recursive" mode
  ltdl, remove bad "recursive" parameter from LT_CONFIG_LTDL_DIR