Fix many warnings.

src/dynamics/mass_properties_capsule.rs

@@ -1,7 +1,7 @@
 use crate::dynamics::MassProperties;
+use crate::math::Point;
 #[cfg(feature = "dim3")]
-use crate::geometry::Capsule;
-use crate::math::{Point, PrincipalAngularInertia, Rotation, Vector};
+use crate::math::Rotation;
 
 impl MassProperties {
     pub(crate) fn from_capsule(density: f32, half_height: f32, radius: f32) -> Self {

src/dynamics/mass_properties_cylinder.rs

@@ -1,7 +1,10 @@
 use crate::dynamics::MassProperties;
+use crate::math::{PrincipalAngularInertia, Vector};
 #[cfg(feature = "dim3")]
-use crate::geometry::Capsule;
-use crate::math::{Point, PrincipalAngularInertia, Rotation, Vector};
+use {
+    crate::geometry::Capsule,
+    crate::math::{Point, Rotation},
+};
 
 impl MassProperties {
     pub(crate) fn cylinder_y_volume_unit_inertia(

src/dynamics/mass_properties_polygon.rs

@@ -1,3 +1,5 @@
+#![allow(dead_code)] // TODO: remove this
+
 use crate::dynamics::MassProperties;
 use crate::math::Point;