tac can now handle regular, nonseekable files like Linux's
/proc/modules. Before, it would produce no output for such a file.
+ tac would exit immediately upon I/O or temp-file creation failure.
+ Now it continues on, processing any remaining command line arguments.
+
"tail -f" no longer mishandles pipes and fifos. With no operands,
tail now ignores -f if standard input is a pipe, as POSIX requires.
When conforming to POSIX 1003.2-1992, tail now supports the SUSv2 b