[xml] Creation of several tickets related to memory corruptions in libxslt

[Nicolas Grégoire <nicolas gregoire agarri fr>]

Hello,

I spent some time fuzzing the libxslt engine. The following tickets
describe some identified issues with possible security implications:

Off-by-one write in rc4_decrypt
https://bugzilla.gnome.org/show_bug.cgi?id=675917

Read of previously free'd memory when using func:result
https://bugzilla.gnome.org/show_bug.cgi?id=680920

Off-by-one read in pattern parsing
https://bugzilla.gnome.org/show_bug.cgi?id=680924

Nick Wellnhofer has already proposed some patches (that I didn't test
for the moment). Many thanks to him!

Nicolas