Add missing <cstdint> and <cstddef> headers.

[breyerml]

This PR fixes a bug introduced in #188 due to not adding the necessary <cstdint> headers when using inptr_t.

Additionally, as far as I understand the code, the current develop branch exhibits UB or, at best, implementation-defined behavior due to the new error checking introduced in #186. If I only enable, for example, the triad kernel, goldC is never written and, therefore, is equal to 0 (the value of startC in the Stream.h header). However, later, the error is calculate as

T eC = std::fabs(vC - goldC) / std::fabs(goldC);

, which results in a division by zero and sets eC to NaN. In the check function, eC is tested against NaN and reports a failing check, although vC is also zero, in which case the result should be marked as correct.
I added a (ugly) hotfix, but I'm currently unable to implement a better fix due to time constraints.

[breyerml]

Also, if I run:

./omp-stream -s 10000000000 -n 2 --only Triad

all I get is a SegFault.
However, running it with

./omp-stream -s 1000000000 -n 2 --only Triad

gives to correct result.

(Note that our machine has enough RAM for the first call.)

[breyerml]

Ok. The problem with this SegFault is that due to the read_arrays function, the STREAM data must be stored twice. Therefore, we actually have 6 * sizeof(T) * array_size instead of 3 * sizeof(T) * array_size, which is kind of unintuitive, to say the least.