Remove `X-Requested-With` info in XDR example

This is no longer necessary as using `xdr: native` will remove
all custom headers for you by default.
fix typo in docs
Merge branch 'dd-typo' of github.com:smikes/yui3 into smikes-dd-typo
Merge branch 'live-docs' into dev-master
Merge branch 'dev-master' into dev-3.x