Fix edge case in uint->string conversion.

src/lib/_uint.rs

@@ -61,7 +61,7 @@ fn to_str(mutable uint n, uint radix) -> str
 
   let uint r = 1u;
   if (n > r) {
-    while ((r*radix) < n) {
+    while ((r*radix) <= n) {
       r *= radix;
     }
   }

src/test/run-pass/lib-int.rs

@@ -8,6 +8,7 @@ fn test_to_str() {
   check (eq(_int.to_str(1, 10u), "1"));
   check (eq(_int.to_str(-1, 10u), "-1"));
   check (eq(_int.to_str(255, 16u), "ff"));
+  check (eq(_int.to_str(100, 10u), "100"));
 }
 
 fn main() {