Declare lam as an array

Fixes certik#44.

Author: certik

src/best-practices.rst

@@ -444,7 +444,7 @@ memory automatically and it is not possible to create memory leaks.
 For example you can allocate it inside a subroutine::
 
     subroutine foo(lam)
-    real(dp), allocatable, intent(out) :: lam
+    real(dp), allocatable, intent(out) :: lam(:)
     allocate(lam(5))
     end subroutine