The HLSLMacro struct is manually malloc'd, not using new/delete, so the std::string destructor is never called on the instance stored in the class.
Fixed by using a char* allocated by HLSLTree, which will then properly take care of deleting it after parsing is complete.
Fixed a transpile issue with a hack used by some preset authors to set a texture sampler to a different filter/wrap mode, removing the "sampler_state" block entirely now as there's no GLSL equivalent (samplers are solely configured on the application side).
Also consolidated a few vertex types into RenderItem and fixed a few old-school effects like DarkenCenter.
