Configure script provides no feedback during `git submodule update`

[burg]

On a slow or even decent network, the initial update of llvm submodule appears to stall, even it it's just taking a long time. Maybe we should not silence git's squawking during this process?

[brson]

Agreed. We show progress on snapshot dls.

[burg]

Servo will have similar problems if large submodules are added, since it copied rust's submodule logic.

[catamorphism]

"easy" and "wishlist" don't make sense to use together -- changed to "enhancement" :-)

[sanxiyn]

See http://article.gmane.org/gmane.comp.version-control.git/192772

[graydon]

Would be nice but not 0.6-blocking.

[graydon]

still plausible, but the option hasn't been added to the git binaries I see on most of our hosts. We could remove the --quiet we pass?