Added a leap second test to test517

tests/data/test517

@@ -109,6 +109,7 @@ nothing
 80: 20110623 56:34:56 => -1
 81: 20111323 12:34:56 => -1
 82: 20110623 12:34:79 => -1
+83: Wed, 31 Dec 2008 23:59:60 GMT => 1230768000
 </stdout>
 
 # This test case previously testes an overflow case ("2094 Nov 6 =>

tests/libtest/lib517.c

@@ -23,7 +23,7 @@
 
 #include "memdebug.h"
 
-static const char *dates[]={
+static const char * const dates[]={
   "Sun, 06 Nov 1994 08:49:37 GMT",
   "Sunday, 06-Nov-94 08:49:37 GMT",
   "Sun Nov  6 08:49:37 1994",
@@ -115,6 +115,7 @@ static const char *dates[]={
   "20110623 56:34:56",
   "20111323 12:34:56",
   "20110623 12:34:79",
+  "Wed, 31 Dec 2008 23:59:60 GMT", /* leap second */
   NULL
 };