Fix a nasty bug exposed by mktime() when time_t is significantly bigger

than 32 bits.  It was trying to figure out things like the day of week
of when time_t is roughly 2^62 etc.  Make a better guess for the starting
point for the binary search that works on both 32 and 64 bit types.  I have
been using this for a while now.

lib/libc/stdtime/localtime.c

@@ -1475,6 +1475,12 @@ int * const		okayp;
 	** (this works whether time_t is signed or unsigned).
 	*/
 	bits = TYPE_BIT(time_t) - 1;
+	/*
+	 * Limit to 32 bits or the things go crazy
+	 * when it tries to figure out times near 2^62 etc.
+	 */
+	if (bits > 31)
+		bits = 31;
 	/*
 	** If time_t is signed, then 0 is just above the median,
 	** assuming two's complement arithmetic.