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

NEWS

@@ -1,4 +1,4 @@
-GNU tar NEWS - User visible changes. 2014-01-21
+GNU tar NEWS - User visible changes. 2014-01-22
 Please send GNU tar bug reports to <bug-tar@gnu.org>
 
 
@@ -11,14 +11,19 @@ total number of bytes transferred at each checkpoint.
 
 * Extended checkpoint format specification.
 
-New conversion specifiers are implemented:
+New conversion specifiers are implemented.  Some of them take
+optional arguments, supplied in curly braces between the percent
+sign and the specifier letter.
 
-  %d  -  output number of seconds since tar started
-  %T  -  output I/O totals
-  %{FMT}t - output current local time using FMT as strftime(3) format
-            If {FMT} is omitted, use %c
-  %{N}*   - pad output with spaces to the Nth column, or to the 
-            current screen width, if {N} is not given.
+  %d        -  output number of seconds since tar started
+  %{r,w,d}T -  output I/O totals; optional arguments supply prefixes
+               to be used before number of bytes read, written and
+	       deleted, correspondingly.
+  %{FMT}t   -  output current local time using FMT as strftime(3) format
+               If {FMT} is omitted, use %c
+  %{N}*     - pad output with spaces to the Nth column, or to the 
+              current screen width, if {N} is not given.
+  %c        -  a shortcut for "%{%Y-%m-%d %H:%M:%S}t: %ds, %{read,wrote}T%*\r"
 
 
 version 1.27.1 - Sergey Poznyakoff, 2013-11-17