[krbdev.mit.edu #8151] Build errors on OpenWrt/GCC 4.8

[Greg Hudson via RT]

All three of these warnings appear to be false positives.

The cc_file.c warning was worked around by #8026 after a previous 
report.  I apparently didn't mark that issue for pullup.  I can't 
reproduce this warning with gcc 4.8.2, but I don't know if I'm 
triggering the inlining necessary to make the warning appear.

The pkinit_crypto_openssl.c is a false positive because the function 
exits if the loop doesn't terminate at the break statement after 
label_len is initialized.  We haven't worked around this on master as 
far as I can tell.  Initializing label_len may be the only simple 
workaround given the current design of the function.

The krad false positive is probably best fixed by initializing *id = 
0 at the beginning of id_generate().