configure.ac: Fix detection of Large File Support
configure.ac: Fix detection of Large File Support

Support for files over 2 gigabytes has been broken for some time on
32 bit systems and no one noticed.

erikd/libsndfile,erikd/libsndfile,libsndfile/libsndfile,erikd/libsndfile,libsndfile/libsndfile,libsndfile/libsndfile,evpobr/libsndfile,erikd/libsndfile,libsndfile/libsndfile,libsndfile/libsndfile,evpobr/libsndfile,evpobr/libsndfile,evpobr/libsndfile,evpobr/libsndfile,erikd/libsndfile