Entity:

Usage:
**change_style(Window, XOR, AND, OR)**

Changes the stile of the **Window**. The new stile is the old one
modified by **XOR**, **AND** and **OR**.

**XOR** gives bits which have to be reversed. For example if **XOR**
is **5** then bits **1** and **4** will be reversed.

**AND** gives which bits have to be zero. For example if **AND**
is **5** then bits **1** and **4** will be set to zero.

**OR** gives which bits have to be one. For example if **OR**
is **5** then bits **1** and **4** will be set to one.

Actually the result is:
*New_value is ((Old_value xor
XOR) /\ \AND) \/ OR*