Add configure-time detection for SSH_TIME_T_MAX.

Should fix printing cert times exceeding INT_MAX (bz#3329) on platforms
were time_t is a long long.  The limit used is for the signed type, so if
some system has a 32bit unsigned time_t then the lower limit will still
be imposed and we would need to add some way to detect this.  Anyone using
an unsigned 64bit can let us know when it starts being a problem.

configure.ac

@@ -3664,14 +3664,24 @@ if test ! -z "$SONY" ; then
   LIBS="$LIBS -liberty";
 fi
 
-# Check for  long long datatypes
+# Check for long long datatypes
 AC_CHECK_TYPES([long long, unsigned long long, long double])
 
 # Check datatype sizes
 AC_CHECK_SIZEOF([short int])
 AC_CHECK_SIZEOF([int])
 AC_CHECK_SIZEOF([long int])
 AC_CHECK_SIZEOF([long long int])
+AC_CHECK_SIZEOF([time_t], [], [[
+    #include <sys/types.h>
+    #ifdef HAVE_SYS_TIME_H
+    # include <sys/time.h>
+    #endif
+    #ifdef HAVE_TIME_H
+    # include <time.h>
+    #endif
+	]]
+)
 
 # Sanity check long long for some platforms (AIX)
 if test "x$ac_cv_sizeof_long_long_int" = "x4" ; then

defines.h

@@ -304,6 +304,12 @@ typedef long long intmax_t;
 typedef unsigned long long uintmax_t;
 #endif
 
+#if SIZEOF_TIME_T == SIZEOF_LONG_LONG_INT
+# define SSH_TIME_T_MAX LLONG_MAX
+#else
+# define SSH_TIME_T_MAX INT_MAX
+#endif
+
 #ifndef HAVE_U_CHAR
 typedef unsigned char u_char;
 # define HAVE_U_CHAR

misc.c

@@ -2384,7 +2384,7 @@ parse_absolute_time(const char *s, uint64_t *tp)
 }
 
 /* On OpenBSD time_t is int64_t which is long long. */
-#define SSH_TIME_T_MAX LLONG_MAX
+/* #define SSH_TIME_T_MAX LLONG_MAX */
 
 void
 format_absolute_time(uint64_t t, char *buf, size_t len)