* mdemo/Makefile.am: ../libltdl is within $(srcdir)
* libltdl, Makefile.am: added libltdl (a system independent
dlopen wrapper library extracted from mdemo)
* ltmain.in: added -module flag for compiling and linking of
modules. If enabled it compiles always both .o (with -DLT_RENAME)
and .lo files
* mdemo: modified mdemo to work with libltdl
* tests/ltdl*: added tests for libltdl
