Introduce libbuf analogous to toybuf but for use by lib/*.c. Change readfile() semantics to be able to read into an existing buffer, or malloc its own if that's NULL.
diff --git a/lib/lib.h b/lib/lib.h
index 14e14e9..26465ad 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -135,7 +135,7 @@
ssize_t writeall(int fd, void *buf, size_t len);
off_t lskip(int fd, off_t offset);
struct string_list **splitpath(char *path, struct string_list **list);
-char *readfile(char *name);
+char *readfile(char *name, char *buf, off_t len);
void msleep(long miliseconds);
int64_t peek(void *ptr, int size);
void poke(void *ptr, uint64_t val, int size);