Fill out missing Android runtime functions

[brson]

src/rt/rust_android_dummy.cpp contains a bunch of empty stubs for functions that don't exist in bionic.

[yichoi]

being managed at https://github.com/yichoi/rust/commits/arm_latest

[catamorphism]

De-milestoning; nominating for maturity milestone 3, feature-complete.

[graydon]

Accepted for feature complete (predicated on android becoming tier-1 supported-platform)

[emberian]

Still relevant

[metajack]

triage bump. is this still going to be in c++ even with the new runtime?

[pnkfelix]

P-low, not 1.0 blocker.

[lahwran]

What does this affect? How is android code limited by this?

[alexcrichton]

@lahwran we still have a file of stubs and presumably if you use one of those functions you're going to get... some interesting results!

[lahwran]

yes, but what actually uses those in the rust stdlib? what should I avoid?