Enable largefile support as needed for improved portability

Enable largefile support to avoid possible issues with >32-bit inode
numbers and such.

Fixes: https://bugs.gentoo.org/show_bug.cgi?id=550438

Author: mgorny

configure.ac

@@ -64,6 +64,7 @@ m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES])
 
 AC_PROG_CC
 AC_USE_SYSTEM_EXTENSIONS
+AC_SYS_LARGEFILE
 AC_CHECK_FUNCS([readlink])
 AM_CONDITIONAL([HAVE_READLINK], [test $ac_cv_func_readlink = yes])