rename: fix cygwin 1.5.x bugs On cygwin 1.5.x, rename("dir","file") mistakenly succeeded. rename("hard1","hard2") mistakenly reduced the hard link count, such that "hard1" disappears once "hard2" is unlinked. * m4/rename.m4 (gl_FUNC_RENAME): Detect cygwin bugs. * lib/rename.c (rpl_rename): Work around them. * modules/rename (Depends-on): Add same-inode.