Initialize local that receives an error code only if there is actually an error.

uidna_openUTS46 overwrites its error code argument only if
there is actually an error. Hence, if the variable is not initialized to
zero it may seem to the calling code that an error has ocurred. This
diff initializes the variable and re-enables the failing test.

hphp/runtime/ext/ext_intl.cpp

@@ -741,7 +741,7 @@ static Variant php_intl_idn_to_46(CStrRef domain, int64_t options, IdnVariant id
   int32_t     converted_len;
   UIDNA       *uts46;
   UIDNAInfo   info = UIDNA_INFO_INITIALIZER;
-  UErrorCode  status;
+  UErrorCode  status = U_ZERO_ERROR;
 
   // Get UIDNA instance which implements UTS #46.
   uts46 = uidna_openUTS46(options, &status);