Remove code for CUDA below 7.5, update version checks

[SunBlack]

• In *.cu files version number of CUDA is stored in CUDART_VERSION (cuda_runtime_api.h) instead of CUDA_VERSION (cuda.h)
• Remove code for CUDA below CUDA 7.5

Fixes following compile issue I had during building #3140

2>Building NVCC (Device) object gpu/surface/CMakeFiles/pcl_gpu_surface.dir/src/cuda/Release/pcl_gpu_surface_generated_convex_hull.cu.obj
2>convex_hull.cu
2>D:/pcl/gpu/surface/src/cuda/convex_hull.cu(474): warning : function "__all"
2>c:\program files\nvidia gpu computing toolkit\cuda\v10.1\include\device_atomic_functions.h(179): here was declared deprecated ("__all() is not valid on compute_70 and above, and should be replaced with __all_sync().To continue using __all(), specify virtual architecture compute_60 when targeting sm_70 and above, for example, using the pair of compiler options: -arch=compute_60 -code=sm_70.")
2>
2>D:/pcl/gpu/surface/src/cuda/convex_hull.cu(503): warning : function "__ballot"
2>c:\program files\nvidia gpu computing toolkit\cuda\v10.1\include\sm_20_intrinsics.h(405): here was declared deprecated ("__ballot() is not valid on compute_70 and above, and should be replaced with __ballot_sync().To continue using __ballot(), specify virtual architecture compute_60 when targeting sm_70 and above, for example, using the pair of compiler options: -arch=compute_60 -code=sm_70.")
2>
2>D:/pcl/gpu/surface/src/cuda/convex_hull.cu(510): warning : function "__ballot"
2>c:\program files\nvidia gpu computing toolkit\cuda\v10.1\include\sm_20_intrinsics.h(405): here was declared deprecated ("__ballot() is not valid on compute_70 and above, and should be replaced with __ballot_sync().To continue using __ballot(), specify virtual architecture compute_60 when targeting sm_70 and above, for example, using the pair of compiler options: -arch=compute_60 -code=sm_70.")
2>
2>D:/pcl/gpu/surface/src/cuda/convex_hull.cu(474): warning : function "__all"
2>c:\program files\nvidia gpu computing toolkit\cuda\v10.1\include\device_atomic_functions.h(179): here was declared deprecated ("__all() is deprecated in favor of __all_sync() and may be removed in a future release (Use -Wno-deprecated-declarations to suppress this warning).")
2>
2>D:/pcl/gpu/surface/src/cuda/convex_hull.cu(503): warning : function "__ballot"
2>c:\program files\nvidia gpu computing toolkit\cuda\v10.1\include\sm_20_intrinsics.h(405): here was declared deprecated ("__ballot() is deprecated in favor of __ballot_sync() and may be removed in a future release (Use -Wno-deprecated-declarations to suppress this warning).")
2>
2>D:/pcl/gpu/surface/src/cuda/convex_hull.cu(510): warning : function "__ballot"
2>c:\program files\nvidia gpu computing toolkit\cuda\v10.1\include\sm_20_intrinsics.h(405): here was declared deprecated ("__ballot() is deprecated in favor of __ballot_sync() and may be removed in a future release (Use -Wno-deprecated-declarations to suppress this warning).")
...

[SunBlack]

During this PR I found a lot of occurences of __CUDA_ARCH__ - I believe we can remove all checks for this, because we require at minimum CUDA 7.5, which supports CUDA ARCH 2.0 at minimum. As far as I understand this documentation __CUDA_ARCH__ will be always >=200 with CUDA 7.5. All checks in PCL are comparing __CUDA_ARCH__ with 200 or 120 or 110, so we always know the result => dead code => can be removed. Should this part of this PR or another PR after this is merged?

[SergioRAgostinho]

I'm gonna merge this now because this code is not being built on the CI. Just open a new PR.