Update *sum(1)-manpages and mark them as finished and audited

Now that -c behaves correctly, the tools are pretty much done.
Only the manpages were not clear enough what happens when you
specify the c-flag.
This is fixed now.

sha256sum.1

@@ -1,17 +1,32 @@
-.Dd January 30, 2015
+.Dd March 1, 2015
 .Dt SHA256SUM 1
 .Os sbase
 .Sh NAME
 .Nm sha256sum
-.Nd compute SHA256 message digest
+.Nd compute or check SHA-256 message digests
 .Sh SYNOPSIS
 .Nm
 .Op Fl c
 .Op Ar file ...
 .Sh DESCRIPTION
-Print SHA256 (256-bit) checksums. With no file, read standard input.
+.Nm
+writes SHA-256 (256-bit) checksums of each
+.Ar file
+to stdout.
+If no
+.Ar file
+is given
+.Nm
+reads from stdin.
 .Sh OPTIONS
 .Bl -tag -width Ds
 .It Fl c
-Read list of SHA256 checksums from file and check them.
+Read list of SHA-256 checksums from each
+.Ar file
+and check them.
+If no
+.Ar file
+is given
+.Nm
+reads from stdin.
 .El