integer: give Planar64 abs

src/integer.rs

@@ -448,6 +448,10 @@ impl Planar64{
 		self.0
 	}
 	#[inline]
+	pub const fn abs(self)->Self{
+		Self(self.0.abs())
+	}
+	#[inline]
 	pub fn sqrt(&self)->Self{
 		Planar64(unsafe{(((self.0 as i128)<<32) as f64).sqrt().to_int_unchecked()})
 	}