(NO_FILE): New macro. All functions changed to test or assign it rather than

(NO_FILE): New macro.  All functions changed to test or assign it rather than
-1 or (FILE*)NULL.
(krb5_fcc_read_keyblock, krb5_fcc_read_data): Rewrite bounds check.
(BINARY_MODE): Always define.
(setvbuf) [!HAVE_SETVBUF]: Define as macro using setbuf.
(krb5_fcc_open_file): Change file descriptor variable to "f" and combine newly
matching stdio and file sections.  Use setvbuf instead of checking whether to
use setbuf.  Fix bug in merge.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@14717 dc483132-0cff-0310-8789-dd5450dbe970