print more information for closures when `-Zverbose` is given
print more information for closures when `-Zverbose` is given

Ideally, we'd probably print the closure substs themselves actually.

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