magic: import and decompile q_ketsu, q_shu

[j3lee]

The HP drain and MP drain effects, imported and fully decompiled (20 functions, no assembly left). One commit per overlay, then the header lines.

• the two files are the same code; they differ in an include and the hit sound id (7 and 0x1F)
• each overlay starts with a 0x10-byte render descriptor ahead of the code; the model tick copies it from there
• the start function doubles as the overlay entry, so it carries the MAGIC_ name

Each file opens with the attack it belongs to, in the form the other magic files use; an effect several attacks share lists them. Functions are named <Overlay><Thing><Verb> after what they draw or do; data keeps its D_ names. No shared header is changed.