libltdl for MinGW32 and native compilers

[stefan]

Dear list,
  The attached patch is meant to fix problems with the libltdl.dll
under Windows.  It attaches LT_SCOPE to each exported/imported symbol.
Furthermore it changes

#ifdef DLL_EXPORT
# define LT_SCOPE __declspec(dllexport)
#endif
#ifdef LIBLTDL_DLL_IMPORT
# define LT_SCOPE extern __declspec(dllimport)
#endif

into

#ifdef LIBLTDL_DLL_IMPORT
# define LT_SCOPE __declspec(dllimport) extern
#elif defined (DLL_EXPORT)
#  define LT_SCOPE __declspec(dllexport) extern
#endif

This fixes the following problem:  With the above order you *cannot* use
the libltdl.dll from another dll, because the dll would define DLL_EXPORT
and LIBLTDL_DLL_IMPORT concurrently.

Do you agree?  And will you apply the patch?

Thanks in advance,
        address@hidden

patch.diff
Description: libltdl patch