Function string_cleanup

depends/lodepng/lodepng.cpp:297–300

free string pointer and set it to NULL*/

/*free string pointer and set it to NULL*/
static void string_cleanup(char** out) {
  lodepng_free(*out);
  *out = NULL;
}

/*also appends null termination character*/
static char* alloc_string_sized(const char* in, size_t insize) {