bolero-MURAKAMI/Sprout — pull request #23 by kariya-mitsuru (2013-08-26 17:33:17+00:00)
Title: fix sprout::equal for empty range

Sample code below may cause segmentation fault.
```c++
#include
#include

int main()
{
std::vector input;
auto result = sprout::equal(input.begin(), input.end(), input.begin(), input.end());
}
```
Fix this and remove sprout::detail::equal2_impl_ra since it was unnecessary.