Stop warning when doc testing proc macro crates
Stop warning when doc testing proc macro crates

Add the actually_rustdoc option to the session that
is passed  to phase_2_configure_and_expand function
inside the rustdoc test module.

This prevents the warning code from triggering when
parsing proc_macro_derive attributes, just like when
`--test` is normally invoked.

graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust