Use of HT_DEBUG_PRINTF requires namespace inclusion

Any file / block of code that contains HT_DEBUG_PRINTF requires the line using namespace Core. We would ideally like to get rid of that reliance.

[raselneck]

Just so it's easier for me when I go to work on this, can you give me an example of where this happens?

Most of the resource implementations. ht_renderpass_resource.cpp, ht_pipeline_resource.cpp, etc.