Make const-nonconst conv less cursed.

source/numem/mem/ptr.d

@@ -161,23 +161,10 @@ public:
         Moves unique_ptr to this instance.
 
         This is a reuse of copy-constructors, and is unique to unique_ptr.
-
-        This exists for DMD support.
     */
     @trusted
     this(ref const(unique_ptr!T) other) {
-
-        // Free our own refcount if need be
-        if (this.rc) {
-            this.reset();
-        }
-
-        // atomically moves the reference from this unique_ptr to the other unique_ptr reference
-        // after this is done, rc is set to null to make this unique_ptr invalid.
-        atomicStore(this.rc, cast(refcountmg_t!(T)*)other.rc);
-
-        // For LDC2 we'll need to do some more cursed pointer casts to be able to call clear on a const.
-        (cast(unique_ptr!(T)*)&other).clear();
+        this(*(cast(unique_ptr!(T)*)&other));
     }
 
     // Destructor