Revert changes to external files.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

external/libwally-core/src/secp256k1/src/group.h

@@ -45,7 +45,7 @@ static void secp256k1_ge_set_xy(secp256k1_ge *r, const secp256k1_fe *x, const se
 
 /** Set a group element (affine) equal to the point with the given X coordinate
  *  and a Y coordinate that is a quadratic residue modulo p. The return value
- *  is true if and only if a coordinate with the given X coordinate exists.
+ *  is true iff a coordinate with the given X coordinate exists.
  */
 static int secp256k1_ge_set_xquad(secp256k1_ge *r, const secp256k1_fe *x);
 

external/libwally-core/src/secp256k1/src/group_impl.h

@@ -641,7 +641,7 @@ static int secp256k1_gej_has_quad_y_var(const secp256k1_gej *a) {
     }
 
     /* We rely on the fact that the Jacobi symbol of 1 / a->z^3 is the same as
-     * that of a->z. Thus a->y / a->z^3 is a quadratic residue if and only if a->y * a->z
+     * that of a->z. Thus a->y / a->z^3 is a quadratic residue iff a->y * a->z
        is */
     secp256k1_fe_mul(&yz, &a->y, &a->z);
     return secp256k1_fe_is_quad_var(&yz);