Update FIXME numbers

Author: catamorphism

src/rustc/middle/const_eval.rs

@@ -132,7 +132,7 @@ fn classify(e: @expr,
                 classify(base, def_map, tcx)
               }
 
-              // FIXME: #1272, we can probably do something CCI-ish
+              // FIXME: (#3728) we can probably do something CCI-ish
               // surrounding nonlocal constants. But we don't yet.
               ast::expr_path(_) => {
                 match def_map.find(e.id) {

src/rustc/middle/trans/base.rs

@@ -632,7 +632,7 @@ fn cast_shift_rhs(op: ast::binop,
         if lhs_sz < rhs_sz {
             trunc(rhs, lhs_llty)
         } else if lhs_sz > rhs_sz {
-            // FIXME (See discussion at #1570): If shifting by negative
+            // FIXME (#1877: If shifting by negative
             // values becomes not undefined then this is wrong.
             zext(rhs, lhs_llty)
         } else {