* demo/Makefile.am: moved testsuite specific declarations to the end,

* demo/Makefile.am: moved testsuite specific declarations to the end,
  the deplibs check is now optional
* libltdl/configure.in: read libtool --config only once,
  merged AC_SYS_SYMBOL_UNDERSCORE+AC_SYS_NM_PARSE from libtool.m4
* libtool.m4: AC_SYS_SYMBOL_UNDERSCORE+AC_SYS_NM_PARSE were not
  used, lt_dlopen and silent may be empty, AC_SYS_LIBTOOL_CYGWIN
  no longer necessary
* ltconfig.in: NM is already checked in libtool.m4,
* tests/Makefile.am: added deplibs.test
* tests/demo-exec.test, demo-inst.test: removed hell0
* tests/deplibs.test: new test to test the deplibs_check_method