Fix Current Culture to make it travel in async operations

In Windows code we'll already having the current culture travel in
the async operation. this feature was missing in Linux code.

Author: tarekgh

src/mscorlib/corefx/System/Globalization/CultureInfo.cs

@@ -133,6 +133,19 @@ public partial class CultureInfo : IFormatProvider
         //The parent culture.
         private CultureInfo m_parent;
 
+        static AsyncLocal<CultureInfo> s_asyncLocalCurrentCulture; 
+        static AsyncLocal<CultureInfo> s_asyncLocalCurrentUICulture;
+
+        static void AsyncLocalSetCurrentCulture(AsyncLocalValueChangedArgs<CultureInfo> args)
+        {
+            s_currentThreadCulture = args.CurrentValue;
+        }
+
+        static void AsyncLocalSetCurrentUICulture(AsyncLocalValueChangedArgs<CultureInfo> args)
+        {
+            s_currentThreadUICulture = args.CurrentValue;
+        }
+
         //
         // The CultureData  instance that reads the data provided by our CultureData class.
         //
@@ -311,7 +324,13 @@ public static CultureInfo CurrentCulture
                 {
                     throw new ArgumentNullException("value");
                 }
-                s_currentThreadCulture = value;
+                
+                if (s_asyncLocalCurrentCulture == null)
+                {
+                    Interlocked.CompareExchange(ref s_asyncLocalCurrentCulture, new AsyncLocal<CultureInfo>(AsyncLocalSetCurrentCulture), null);
+                }
+                // this one will set s_currentThreadCulture too
+                s_asyncLocalCurrentCulture.Value = value;
             }
         }
 
@@ -355,8 +374,14 @@ public static CultureInfo CurrentUICulture
                 }
 
                 CultureInfo.VerifyCultureName(value, true);
+                
+                if (s_asyncLocalCurrentUICulture == null)
+                {
+                    Interlocked.CompareExchange(ref s_asyncLocalCurrentUICulture, new AsyncLocal<CultureInfo>(AsyncLocalSetCurrentUICulture), null);
+                }
 
-                s_currentThreadUICulture = value;
+                // this one will set s_currentThreadUICulture too
+                s_asyncLocalCurrentUICulture.Value = value;               
             }
         }