Sequence: Specialise compute_sequence_values for builtin arithmetic types

[bjude]

Only explicitly cast to T when we're dealing with builtin arithmetic types and just perform the init + step * i operation for all other types. This enables thrust::sequence to work for types without a conversion from std::size_t.

Addresses issue #1498

[GPUtester]

Can one of the admins verify this patch?

[alliepiper]

Thanks for the patch, and sorry about the review delay!

LGTM -- I just pushed a small fixup commit to add a missing newline. Starting tests now.

DVS CL: 30441766

run tests

[alliepiper]

There are some build failures to address before this is merged:

../testing/sequence.cu: In function 'void TestSequenceNoSizeTConversion()':
../testing/sequence.cu:152:20: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (auto i = 0; i < m.size(); ++i)
                      ~~^~~~~~~~~~

We also need to support C++11, so the enable_if_t will need to be changed to enable_if.

../thrust/system/detail/generic/sequence.inl:69:34: error: ‘enable_if_t’ is not a member of ‘std’
 struct compute_sequence_value<T, std::enable_if_t<std::is_arithmetic<T>::value>>
                                  ^~~

[alliepiper]

Thanks for the quick fix :) Restarting tests.

DVS CL: 30452736

run tests

[bjude]

Damn, that one didnt show up with MSVC, they seem to be a bit inconsistent with when the signed vs unsigned warning triggers.

I'll get it fixed up today

[alliepiper]

Thanks!

DVS CL: 30482082

run tests