`rtcore_config.h.in does` not define `RTC_NAMESPACE` when `EMBREE_API_NAMESPACE` is not defined when it should be defined but empty. This can cause a problem with forward declarations like the following:
```c++
RTC_NAMESPACE_BEGIN
typedef struct RTCSceneTy* RTCScene;
RTC_NAMESPACE_END
void my_function(RTC_NAMESPACE::RTCScene scene);
```
Added alignment definitions to RTCHitNt and RTCRayNt templates so they match the C definitions provided. As the alignment calculation is nasty without requiring the alignof keyword, or constexpr functions, this could instead be hidden behind a macro. Maybe RTC_ALIGN_SOA_AT_LEAST(N, MIN)?
The code is equivalent to:
```
constexpr std::size_t AlignSOAAtLeast(unsigned N, std::size_t min_alignment) noexcept {
if (std::has_single_bit<unsigned>(N)) {
return std::max<std::size_t>(min_alignment, N * alignof(float));
} else {
return min_alignment;
}
}
```
Checking this works is as simple as adding a few static assertions:
```
static_assert(alignof(embree::RTCRayNt<1>) == alignof(embree::RTCRay));
static_assert(alignof(embree::RTCRayNt<4>) == alignof(embree::RTCRay4));
static_assert(alignof(embree::RTCRayNt<8>) == alignof(embree::RTCRay8));
static_assert(alignof(embree::RTCRayNt<16>) == alignof(embree::RTCRay16));
```
Daniel Simon