Unit test arbitrarily long ungetc()

tests/Makefile

@@ -42,6 +42,7 @@ EXPECT_NAMES=\
 	stdio/setvbuf \
 	stdio/sprintf \
 	stdio/printf_space_pad \
+	stdio/ungetc_multiple \
 	stdlib/a64l \
 	stdlib/alloc \
 	stdlib/atof \

tests/expected/stdio/ungetc_multiple.stdout

+hello world

tests/stdio/ungetc_multiple.c

+#include <stdio.h>
+int main() {
+  ungetc('\n', stdin);
+  ungetc('d', stdin);
+  ungetc('l', stdin);
+  ungetc('r', stdin);
+  ungetc('o', stdin);
+  ungetc('w', stdin);
+  ungetc(' ', stdin);
+  ungetc('o', stdin);
+  ungetc('l', stdin);
+  ungetc('l', stdin);
+  ungetc('e', stdin);
+  ungetc('h', stdin);
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+  putchar(getchar());
+}