Implement statistics display in checkpoint actions.

* NEWS: Update.
* configure.ac: Version 1.27.90
* gnulib.modules: Add fprintftime.
* doc/tar.texi: Document the "totals" action and new format specifiers
for echo and ttyout checkpoint actions.
* src/buffer.c (compute_duration): Return computed value.
(print_stats): Don't print trailing newline.  Return number of
characters output.
(format_total_stats): New function.
(print_total_stats): Rewrite via format_total_stats.
* src/checkpoint.c (checkpoint_opcode) <cop_totals>: New opcode.
(checkpoint_compile_action): Handle cop_totals.
(expand_checkpoint_string): Remove.
(format_checkpoint_string): New function to be used instead of
expand_checkpoint_string.  All callers updated.
* src/common.h (TF_READ,TF_WRITE)
(TF_DELETED): New constants.
(format_total_stats,print_total_stats): New protos.
Improve checkpoint interface.

* src/buffer.c (format_total_stats): The format arg is const
All uses updated.
(default_total_format): const
* src/checkpoint.c (tty, tty_cleanup): New static.
(format_checkpoint_string): New "canned" format %c
(checkpoint_finish): New function.
* src/common.h (checkpoint_finish): New proto.
* src/tar.c (main): Call checkpoint_finish.`
checkpoint actions: further improvements.

* NEWS: Update.
* doc/tar.texi: Update.
* src/buffer.c (print_stats): Avoid use of additional string buffer.
Allow for text to be NULL.
Call gettext if it is not.
(format_total_stats): Don't use gettext when calling print_stats.
* src/checkpoint.c (def_format): Change default format.
(format_checkpoint_string): Implement optional arguments for
T conversion.
(finish_checkpoint_actions): Rename to checkpoint_flush_actions,
make extern.  All uses changed.
* src/common.h (checkpoint_flush_actions): New proto.
* src/tar.c (main): Set error_hook