[PATCH]Clean up: using "%m" instead of "%s + strerror(errno)"

[HARA Hiroshi]

Hi,

I found that some codes use "%m" and some other code
use "%s + strerror(errno)" to show error message.
so I clean up the whole code to use "%m" instead of
"%s + strerror(errno)".

this patch is not bug fix or enhancement,
but I feel it is better to use one rule in whole code.

I'd appreciate it if you could review this attached patch.

thank you,