renderer_opengl: Refactor shader generation/caching to be more organized + various cleanups.

src/common/common_funcs.h

@@ -4,6 +4,9 @@
 
 #pragma once
 
+#include <cstddef>
+#include <functional>
+
 #include "common_types.h"
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
@@ -95,3 +98,18 @@ inline u64 _rotr64(u64 x, unsigned int shift){
 // This function might change the error code.
 // Defined in Misc.cpp.
 const char* GetLastErrorMsg();
+
+template <typename T>
+inline std::size_t hash(const T& o) {
+    return std::hash<T>()(o);
+}
+
+template <typename T>
+inline std::size_t combine_hash(const T& o) {
+    return hash(o);
+}
+
+template <typename T, typename... Args>
+inline std::size_t combine_hash(const T& o, const Args&... args) {
+    return hash(o) * 3 + combine_hash(args...);
+}