Convert existing die(..., strerror(errno)) to die_errno()

Change calls to die(..., strerror(errno)) to use the new die_errno().

In the process, also make slight style adjustments: at least state
_something_ about the function that failed (instead of just printing
the pathname), and put paths in single quotes.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

test-sha1.c

@@ -32,7 +32,7 @@ int main(int ac, char **av)
 			if (sz == 0)
 				break;
 			if (sz < 0)
-				die("test-sha1: %s", strerror(errno));
+				die_errno("test-sha1");
 			this_sz += sz;
 			cp += sz;
 			room -= sz;