Warnings in server_stubs.c (signed vs unsigned errmsg, gcc printf)

Warnings in server_stubs.c (signed vs unsigned errmsg, gcc printf)

server_stubs.c uses char * for error messages which it gets from com_err,
throwing away the constness of the com_err output.  Made error message args
be const char * to remove warnings and prevent accidental modification of
com_err strings.

In calls to krb5_klog_syslog server_stubs.c passes void* into %s printf
formats and passes size_ts in for the field widths in %.*s formats.  After
verifying that the size_ts cannot be bigger than ints (which is ensured by
trunc_name) added casts to remove spurious warnings.

ticket: new

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@20344 dc483132-0cff-0310-8789-dd5450dbe970