fix a bug caused by intel compiler

Author: dzzz2001

source/source_base/ylm.cpp

@@ -808,9 +808,9 @@ void Ylm::rl_sph_harm
 void Ylm::grad_rl_sph_harm
 (
  	const int& Lmax, //max momentum of L
- 	const double& x,
-	const double& y,
-	const double& z,
+ 	const double x,
+	const double y,
+	const double z,
 	double* rly,
 	double** grly
 )

source/source_base/ylm.h

@@ -124,9 +124,9 @@ class Ylm
 	 */
 	static void grad_rl_sph_harm(
 			const int& Lmax,
-			const double& x,
-			const double& y,
-			const double& z,
+			const double x,
+			const double y,
+			const double z,
 			double* rly,
 			double** grly);