Correct a bug in the P function: according to 7th edition UNIX (tm), the

newline must be part of the pattern space i.e. `echo a|sed -e P' must print
a
a
and not
aa
This is consistent with gnu sed, SunOS, Ultrix (and probably others!)

usr.bin/sed/process.c

@@ -180,7 +180,7 @@ process()
 				if (pd)
 					break;
 				if ((p = memchr(ps, '\n', psl)) != NULL) {
-					oldc = *p;
+					oldc = *++p;
 					*p = '\0';
 				}
 				OUT(ps)