See comment and
<https://gitlab.com/libeigen/eigen/merge_requests/46#note_270622952>.

See comment for details.

See
<https://stackoverflow.com/questions/59709148/ensuring-that-eigen-uses-avx-vectorization-for-a-certain-operation>
for an explanation of the problem this solves.

In short, for some reason, before this commit the half-packet is
selected when the array / matrix size is not a multiple of
`unpacket_traits<PacketType>::size`, where `PacketType` starts out
being the full Packet.

For example, for some data of 100 `float`s, `Packet4f` will be
selected rather than `Packet8f`, because 100 is not a multiple of 8,
the size of `Packet8f`.

This commit switches to selecting the half-packet if the size is
less than the packet size, which seems to make more sense.

As I stated in the SO post I'm not sure that I'm understanding the
issue correctly, but this fix resolves the issue in my program. Moreover,
`make check` passes, with the exception of line 614 and 616 in
`test/packetmath.cpp`, which however also fail on master on my machine:

    CHECK_CWISE1_IF(PacketTraits::HasBessel, numext::bessel_i0, internal::pbessel_i0);
    ...
    CHECK_CWISE1_IF(PacketTraits::HasBessel, numext::bessel_i1, internal::pbessel_i1);

Remove rogue include in TypeCasting.h. Meta.h is already included by the top-level header in Eigen/Core.

Bug #1790: Make `areApprox` check `numext::isnan` instead of bitwise equality (NaNs don't have to be bitwise equal).

Refactor shared packetmath code to header file.
(Squashed from PR !38)

call Explicitly ::rint and ::rintf for targets without c++11. Without this, the Windows build breaks when trying to compile numext::rint<double>.

InterpolateWithDerivative does not initialize the be vector correctly. This issue is discussed In stackoverflow question 48382939.

Don't use the rational approximation to the logistic function on GPUs as it appears to be slightly slower.

The upper limits for where to use the rational approximation to the logistic function were not set carefully enough in the original commit, and some arguments would cause the function to return values greater than 1. This change set the versions found by scanning all floating point numbers (using std::nextafterf()).

This provides a new op that matches std::rint and previous behavior of
pround. Also adds corresponding unsupported/../Tensor op.
Performance is the same as e. g. floor (tested SSE/AVX).

 * Adding Missing operations for vector comparison in SYCL. This caused compiler error for vector comparison when compiling SYCL
 * Fixing the compiler error for placement new in TensorForcedEval.h This caused compiler error when compiling SYCL backend
 * Reducing the SYCL warning by  removing the abort function inside the kernel
 * Adding Strong inline to functions inside SYCL interop.

The breakage was introduced by the following commit :

https://gitlab.com/libeigen/eigen/commit/ae07801dd8d295657f28b006e1e4999edf835052

After the commit, HIPCC errors out on some tests with the following error

```
Building HIPCC object unsupported/test/CMakeFiles/cxx11_tensor_device_1.dir/cxx11_tensor_device_1_generated_cxx11_tensor_device.cu.o
In file included from /home/rocm-user/eigen/unsupported/test/cxx11_tensor_device.cu:17:
In file included from /home/rocm-user/eigen/unsupported/Eigen/CXX11/Tensor:100:
/home/rocm-user/eigen/unsupported/Eigen/CXX11/src/Tensor/TensorBlock.h:129:12: error: no matching constructor for initialization of 'Eigen::internal::TensorBlockResourceRequirements'
    return {merge(lhs.shape_type, rhs.shape_type),           // shape_type
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/rocm-user/eigen/unsupported/Eigen/CXX11/src/Tensor/TensorBlock.h:75:8: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 3 were provided
struct TensorBlockResourceRequirements {
       ^
/home/rocm-user/eigen/unsupported/Eigen/CXX11/src/Tensor/TensorBlock.h:75:8: note: candidate constructor (the implicit move constructor) not viable: requires 1 argument, but 3 were provided
/home/rocm-user/eigen/unsupported/Eigen/CXX11/src/Tensor/TensorBlock.h:75:8: note: candidate constructor (the implicit copy constructor) not viable: requires 5 arguments, but 3 were provided
/home/rocm-user/eigen/unsupported/Eigen/CXX11/src/Tensor/TensorBlock.h:75:8: note: candidate constructor (the implicit default constructor) not viable: requires 0 arguments, but 3 were provided
...
...
```

The fix is to explicitly decalre the (implicitly called) constructor as a device func

This fixes deprecated-copy warnings when compiling with GCC>=9
Also protect some additional Base-constructors from getting called by user code code (#1587)