Revert "Expand macros and quoted variables inside << >>, closes #1063"

It broke the build. Reopens #1063.

This reverts commit 93f71c86242155fc026c2f814947e77621714432.
Add missing unquote/unquote_splicing documentation
Expand macros and quoted variables inside << >>, closes #1063
Ensure record args are evaluated in the parent context, closes #1065
Implement capture_io for ex_unit