Amulet of magical breathing increases energy regen

Normally energy regen is 1d2 or 1d3, so wearing the amulet increases
that to 1d4 or 1d5.  The only way to get energy regeneration is via
The Eye of the Aethiopica, so you cannot have both at the same time.

src/allmain.c

@@ -607,6 +607,9 @@ regen_pw(int wtcap)
                               / 6)))) || Energy_regeneration)) {
         int upper = (int) (ACURR(A_WIS) + ACURR(A_INT)) / 15 + 1;
 
+        if (EMagical_breathing)
+            upper += 2;
+
         u.uen += rn1(upper, 1);
         if (u.uen > u.uenmax)
             u.uen = u.uenmax;