rxkad: Resolve warnings in ticket5.c

rxkad: Resolve warnings in ticket5.c

Resolves these warnings:

ticket5.c: In function ‘tkt_MakeTicket5’:
ticket5.c:574:33: warning: pointer targets in passing argument 1 of ‘_rxkad_v5_encode_EncTicketPart’ differ in signedness [-Wpointer-sign]
     code = encode_EncTicketPart(encodebuf, allocsiz, &data, &encodelen);
                                 ^
In file included from ticket5.c:80:0:
v5gen-rewrite.h:43:30: note: expected ‘unsigned char *’ but argument is of type ‘char *’
 #define encode_EncTicketPart _rxkad_v5_encode_EncTicketPart
                              ^
v5gen.c:1889:1: note: in expansion of macro ‘encode_EncTicketPart’
 encode_EncTicketPart(unsigned char *p, size_t len, const EncTicketPart * data, size_t * size)
 ^
ticket5.c:602:33: warning: pointer targets in passing argument 1 of ‘_rxkad_v5_encode_EncryptedData’ differ in signedness [-Wpointer-sign]
     code = encode_EncryptedData(ticket + *ticketLen - 1, *ticketLen, &encdata, &tl);
                                 ^
In file included from ticket5.c:80:0:
v5gen-rewrite.h:16:30: note: expected ‘unsigned char *’ but argument is of type ‘char *’
 #define encode_EncryptedData _rxkad_v5_encode_EncryptedData
                              ^
v5gen.c:690:1: note: in expansion of macro ‘encode_EncryptedData’
 encode_EncryptedData(unsigned char *p, size_t len, const EncryptedData * data, size_t * size)
 ^
ticket5.c: In function ‘tkt_DecodeTicket5’:
ticket5.c:320:10: warning: ‘plainsiz’ may be used uninitialized in this function [-Wmaybe-uninitialized]
     code = decode_EncTicketPart((unsigned char *)plain, plainsiz, &decr_part, &siz);
          ^

Change-Id: Ic1b878f01cf82222dc258847747ce192ee5948fc
Reviewed-on: http://gerrit.openafs.org/11955
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>