Added rect draw api

Added some new maths types
Updated shaders to use new D_Rect structure
Added rect buffers to frames
Misc cleanup

code/vulkan/functions.h

@@ -62,6 +62,8 @@
 	VK_FUNC(CmdDraw);
 	VK_FUNC(CmdSetViewport);
 	VK_FUNC(CmdSetScissor);
+	VK_FUNC(CmdDrawIndexed);
+	VK_FUNC(CmdBindIndexBuffer);
 
 	VK_FUNC(CmdPushConstants);
 	VK_FUNC(CmdCopyBufferToImage);