hexdump: fix dup block comparison

function                                             old     new   delta
bb_dump_dump                                        1523    1520      -3

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

testsuite/hexdump.tests

@@ -15,4 +15,23 @@ testing 'hexdump -C with four NULs' \
 	'' \
 	'\0\0\0\0'
 
+testing "hexdump does not think last padded block matches any full block" \
+	"hexdump -e '1/1 \"%02x|\"1/1 \"%02x!\\n\"'" \
+	"\
+00|00!
+*
+00|  !
+" \
+	'' \
+	'\0\0\0\0\0\0\0\0\0\0\0'
+
+testing "hexdump thinks last full block can match" \
+	"hexdump -e '1/1 \"%02x|\"1/1 \"%02x!\\n\"'" \
+	"\
+00|00!
+*
+" \
+	'' \
+	'\0\0\0\0\0\0\0\0\0\0\0\0'
+
 exit $FAILCOUNT