Now all the code used to manipulate chunks uses a struct buffer instead.
The functions are still called "chunk*", and some of them will progressively
move to the generic buffer handling code as they are cleaned up.
It already returns an empty string when the field is empty, but as a
preventive measure we should do the same when the string itself is a
NULL. While it is not supposed to happen, it will make the code more
resistant against failed allocations and unexpected results.
This fix should be backported to 1.7.
Move the "show stat" command to stats.c using the CLI keyword API
to register it on the CLI. The stats_dump_stat_to_buffer() function
is now static again.
proto/dumpstats.h has been split in 4 files:
* proto/cli.h contains protypes for the CLI
* proto/stats.h contains prototypes for the stats
* types/cli.h contains definition for the CLI
* types/stats.h contains definition for the stats
