change xor in aes.c to xxor
change xor in aes.c to xxor

I actually got a very cryptic error about invalid lambda functions on
this.  It puzzled me for a bit before I realized you can't name a
variable "xor" in C++... it's a keyword.

mbk/ren-c,hostilefork/rebol,giuliolunati/ren-c,rgchris/ren-c,hostilefork/rebol,codebybrett/ren-c,giuliolunati/ren-c,kealist/ren-c,hostilefork/rebol,kealist/ren-c,kealist/ren-c,draegtun/ren-c,mbk/ren-c,mbk/ren-c,mbk/ren-c,kealist/ren-c,rgchris/ren-c,kealist/ren-c,draegtun/ren-c,giuliolunati/ren-c,hostilefork/rebol,codebybrett/ren-c,draegtun/ren-c,codebybrett/ren-c,hostilefork/rebol,rgchris/ren-c,draegtun/ren-c,draegtun/ren-c,hostilefork/rebol,codebybrett/ren-c,giuliolunati/ren-c,giuliolunati/ren-c,rgchris/ren-c,codebybrett/ren-c,rgchris/ren-c,kealist/ren-c,draegtun/ren-c,codebybrett/ren-c