Improve error handling in the btrfs command

Improve error handling in the btrfs command

Hi Chris,

below is enclosed a trivial patch, which has the aim to improve the error
reporting of the "btrfs" command.

You can pull from

	http://cassiopea.homelinux.net/git/btrfs-progs-unstable.git

branch

	strerror

I changed every printf("some-error") to something like:

	e = errno;
	fprintf(stderr, "ERROR: .... - %s", strerror(e));

so:

1) all the error are reported to standard error
2) At the end of the message is printed the error as returned by the system.

The change is quite simple, I replaced every printf("some-error") to the line
above. I don't touched anything other.
I also integrated a missing "printf" on the basis of the Ben patch.

This patch leads the btrfs command to be more "user friendly" :-)

Regards
G.Baroncelli

 btrfs-list.c |   40 ++++++++++++++++++++++--------
 btrfs_cmds.c |   77 ++++++++++++++++++++++++++++++++++++++++-----------------
 utils.c      |    6 ++++
 3 files changed, 89 insertions(+), 34 deletions(-)

Signed-off-by: Chris Mason <chris.mason@oracle.com>