Test failures for old Intel arch

[wolfv]

There are some small failures with loading 64bit integers from char for -arch=nocona

[ RUN      ] xsimd.api_load
1: lhs = 67305985 - rhs = 1
2: lhs = 134678021 - rhs = 2
load uchar   -> int64  : BAD
Nb diff  : 2 (100%)
1: lhs = 67305985 - rhs = 1
2: lhs = 134678021 - rhs = 2
loadu uchar  -> int64  : BAD
Nb diff  : 2 (100%)
/home/wolfv/Programs/xsimd/test/xsimd_api_test.cpp:70: Failure
Value of: res
  Actual: false
Expected: true
[  FAILED  ] xsimd.api_load (0 ms)

and

[ RUN      ] xsimd.sse_load
1: lhs = 67305985 - rhs = 1
2: lhs = 134678021 - rhs = 2
load uchar  -> int64  : BAD
Nb diff  : 2 (100%)