clean up stdio_impl.h
this header evolved to facilitate the extremely lazy practice of
omitting explicit includes of the necessary headers in individual
stdio source files; not only was this sloppy, but it also increased
build time.
now, stdio_impl.h is only including the headers it needs for its own
use; any further headers needed by source files are included directly
where needed.
diff --git a/src/stdio/ftell.c b/src/stdio/ftell.c
index 3904a1d..82371e3 100644
--- a/src/stdio/ftell.c
+++ b/src/stdio/ftell.c
@@ -1,4 +1,6 @@
#include "stdio_impl.h"
+#include <limits.h>
+#include <errno.h>
off_t __ftello_unlocked(FILE *f)
{