[2.1] Update redismodule.h (#409)

* Update redismodule.h

(cherry picked from commit 0c2c70f)

* Remove commented out code

(cherry picked from commit ab4c242)

* Add missing new line

(cherry picked from commit 88c170a)

Author: oshadmi

src/configuration.rs

@@ -34,6 +34,9 @@ bitflags! {
 
         /// For enum configs, this config will allow multiple entries to be combined as bit flags.
         const BITFLAGS = raw::REDISMODULE_CONFIG_BITFLAGS;
+
+        /// For configs, will avoid prefixing the config name with the module name.
+        const UNPREFIXED = raw::REDISMODULE_CONFIG_UNPREFIXED;
     }
 }