lseek: port around macOS SEEK_DATA glitch Problem reported by Sudhip Nashi (Bug#51857). * doc/posix-functions/lseek.texi (lseek): Mention macOS SEEK_DATA issue. * lib/lseek.c (rpl_lseek): Work around macOS portability glitch. * m4/lseek.m4 (gl_FUNC_LSEEK): Replace lseek on Darwin. * modules/lseek (Depends-on): Depend on msvc-nothrow and fstat only if needed.