detect-xor: do not depend on C code

[inashivb]

@catenacyber one of the exhibits of the problem you mentioned 🥲

[catenacyber]

Nice find, how did you find it ?

[inashivb]

Nice find, how did you find it ?

Was just trying to reproduce the memleak issue you fixed w xor transform..

[catenacyber]

So, there are a lot more :

git grep '\- src/' | cut -d: -f2- | cut -d/ -f2- | sort | uniq -c
   4 detect-transform-casechange.c
   3 detect-transform-dotprefix.c
   1 detect-transform-xor.c

[catenacyber]

git grep '\- src/' | cut -d: -f2- | cut -d/ -f2- | sort | uniq | while read i; do echo -n $i; ls ../../suricata/src/$i; done | grep No full one-liner

[inashivb]

Please consider PR #2143 instead of this. That one is more complete.