Rewrite platform_is_steam_overlay_attached for Unix to detect all possible situations

src/platform/unix.c

@@ -43,8 +43,35 @@ char platform_get_path_separator()
 }
 */
 
+// See http://syprog.blogspot.ru/2011/12/listing-loaded-shared-objects-in-linux.html
+struct lmap {
+	void* base_address;
+	char* path;
+	void* unused;
+	struct lmap *next, *prev;
+};
+
+struct dummy {
+	void* pointers[3];
+	struct dummy* ptr;
+};
+
 bool platform_is_steam_overlay_attached() {
-	return dlopen("gameoverlayrenderer.so", RTLD_NOW | RTLD_NOLOAD) != NULL;
+	void* processHandle = dlopen(NULL, RTLD_NOW);
+
+	struct dummy* p = (struct dummy*) processHandle;
+	p = p->ptr;
+
+	struct lmap* pl = (struct lmap*) p->ptr;
+
+	while (pl != NULL) {
+		if (strstr(pl->path, "gameoverlayrenderer.so") != NULL) {
+			return true;
+		}
+		pl = pl->next;
+	}
+
+	return false;
 }
 
 #endif