Adds:
.setxattr
.getxattr
.listxattr
.removexattr
This is the raw patch from the quick implementation I've made. Of note:
- the bulk of the code is in a separate file, xattr.c; this makes no attempt to separate queries from the top level. It should be relatively easy to #ifdef the code out.
- it adds a few "#include"s to log.h and query.h to support loading those from a file which...
