Add vector.combine (#11920)

doc/client_lua_api.txt

@@ -580,6 +580,7 @@ Spatial Vectors
 * `vector.floor(v)`: returns a vector, each dimension rounded down
 * `vector.round(v)`: returns a vector, each dimension rounded to nearest int
 * `vector.apply(v, func)`: returns a vector
+* `vector.combine(v, w, func)`: returns a vector
 * `vector.equals(v1, v2)`: returns a boolean
 
 For the following functions `x` can be either a vector or a number:

doc/lua_api.txt

@@ -3409,6 +3409,9 @@ vectors are written like this: `(x, y, z)`:
 * `vector.apply(v, func)`:
     * Returns a vector where the function `func` has been applied to each
       component.
+* `vector.combine(v, w, func)`:
+	* Returns a vector where the function `func` has combined both components of `v` and `w`
+	  for each component
 * `vector.equals(v1, v2)`:
     * Returns a boolean, `true` if the vectors are identical.
 * `vector.sort(v1, v2)`: