add new error files

add the error files from sdl_template.
they are called 'error' instead of 'errors'.
'error' shall replace 'errors' in a following commit

src/error.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdnoreturn.h>
+
+/* defines statuses in the 0..127, any higher/negative values are POSIX-reserved.
+ * The max value (or -1) shall mean the application is running, anything else shall mean an exit code of some kind */
+enum {
+    // clang-format off
+    STATUS_SUCCESS = 0,                // 0; successful exit
+    STATUS_ERROR   = 1,                // miscellaneous error
+    ERROR_INIT     = STATUS_ERROR | 2, // initialisation error
+
+    ERROR_STD             = STATUS_ERROR   | 64, // standard library error
+    ERROR_STD_INIT        = ERROR_INIT     | 64, // standard library initialisation error
+    ERROR_STD_MEMORY      = ERROR_STD      | 32, // memory error
+    ERROR_STD_MEMORY_INIT = ERROR_STD_INIT | 32, // memory initialization error
+
+    ERROR_SDL                = STATUS_ERROR   | 32, // SDL error
+    ERROR_SDL_INIT           = ERROR_INIT     | 32, // SDL initialization error
+    ERROR_SDL_RENDERING      = ERROR_SDL      | 16, // rendering error
+    ERROR_SDL_RENDERING_INIT = ERROR_SDL_INIT | 16, // rendering initialization error
+    ERROR_SDL_AUDIO          = ERROR_SDL      | 8,  // audio error
+    ERROR_SDL_AUDIO_INIT     = ERROR_SDL_INIT | 8,  // audio initialization error
+
+    STATUS_RUNNING = -1,
+    // clang-format on
+};
+typedef int8_t gamestatus;
+
+void set_gamestatus(gamestatus); // sets the current status of the game
+gamestatus get_gamestatus(void); // gets the current status of the game
+void debug(char const*, ...);    // prints a debug message to stdout if the DEBUG environment variable is set, otherwise the call is ignored.
+void info(char const*, ...);     // prints an info message to stdout
+void warn(char const*, ...);     // prints a warning message to stderr
+void error(char const*, ...);    // prints an warning message to stderr
+
+// prints an error message to stderr before exiting
+noreturn void fatal(gamestatus, char const* file_name, uint32_t line, char const* fmt, ...);