Fix HTTPServer gpu-renderer interfacing

Fixing some compilation issues that occur when enabling the HTTP server

include/PICA/gpu.hpp

@@ -85,6 +85,7 @@ class GPU {
 	GPU(Memory& mem, EmulatorConfig& config);
 	void initGraphicsContext() { renderer->initGraphicsContext(); }
 	void display() { renderer->display(); }
+	void screenshot(const std::string& name) { renderer->screenshot(name); }
 
 	void fireDMA(u32 dest, u32 source, u32 size);
 	void reset();

include/renderer.hpp

@@ -27,6 +27,8 @@ class Renderer {
 	virtual void displayTransfer(u32 inputAddr, u32 outputAddr, u32 inputSize, u32 outputSize, u32 flags) = 0;  // Perform display transfer
 	virtual void drawVertices(PICA::PrimType primType, std::span<const PICA::Vertex> vertices) = 0;             // Draw the given vertices
 
+	virtual void screenshot(const std::string& name) = 0;
+
 	virtual void setFBSize(u32 width, u32 height) = 0;
 
 	virtual void setColourFormat(PICA::ColorFmt format) = 0;

include/renderer_gl/renderer_gl.hpp

@@ -1,7 +1,8 @@
 #pragma once
+#include <stb_image_write.h>
+
 #include <array>
 #include <span>
-#include <stb_image_write.h>
 
 #include "PICA/float_types.hpp"
 #include "PICA/pica_vertex.hpp"