tree-wide: never use the off_t unless glibc makes us use it

off_t is a really weird type as it is usually 64bit these days (at least
in sane programs), but could theoretically be 32bit. We don't support
off_t as 32bit builds though, but still constantly deal with safely
converting from off_t to other types and back for no point.

Hence, never use the type anymore. Always use uint64_t instead. This has
various benefits, including that we can expose these values directly as
D-Bus properties, and also that the values parse the same in all cases.

src/basic/util.h

@@ -152,7 +152,7 @@ void close_many(const int fds[], unsigned n_fd);
 int fclose_nointr(FILE *f);
 FILE* safe_fclose(FILE *f);
 
-int parse_size(const char *t, off_t base, off_t *size);
+int parse_size(const char *t, uint64_t base, uint64_t *size);
 
 int parse_boolean(const char *v) _pure_;
 int parse_pid(const char *s, pid_t* ret_pid);
@@ -478,7 +478,7 @@ bool kexec_loaded(void);
 
 int prot_from_flags(int flags) _const_;
 
-char *format_bytes(char *buf, size_t l, off_t t);
+char *format_bytes(char *buf, size_t l, uint64_t t);
 
 int fd_wait_for_event(int fd, int event, usec_t timeout);