Quash a whole bunch of warnings

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@145624 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/future.cpp b/src/future.cpp
index ff59110..d5c55b6 100644
--- a/src/future.cpp
+++ b/src/future.cpp
@@ -152,9 +152,9 @@
 {
     if (!__is_ready())
     {
-        if (__state_ & deferred)
+        if (__state_ & static_cast<unsigned>(deferred))
         {
-            __state_ &= ~deferred;
+            __state_ &= ~static_cast<unsigned>(deferred);
             __lk.unlock();
             __execute();
         }