Misc Improvements to GPU Package

- Optimizations for molecular systems
-   Improved kernel performance and greater CPU overlap
- Reduced GPU to CPU communications for discrete devices
- Switch classic Intel makefiles to use LLVM-based compilers
- Prefetch optimizations supported for OpenCL
- Optimized data repack for quaternions

lib/gpu/lal_atom.cu

@@ -18,7 +18,7 @@
 #endif
 
 __kernel void kernel_cast_x(__global numtyp4 *restrict x_type,
-                            const __global numtyp *restrict x,
+                            const __global double *restrict x,
                             const __global int *restrict type,
                             const int nall) {
   int ii=GLOBAL_ID_X;