auto merge of #9664 : alexcrichton/rust/logging, r=huonw

This makes some headway on #3309, see commits for details.

diff --cc src/librustc/middle/trans/expr.rs
Simple merge

diff --cc src/librustc/rustc.rs
Simple merge

diff --cc src/libstd/rt/logging.rs
Simple merge

diff --cc src/rt/rust_builtin.cpp
Simple merge

diff --cc src/rt/rustrt.def.in
index 30f60c662e991c797fc436178fa605a47f2390d9,f622b5dbb148eae28d51dedfc9e24ae81a857f64..959d1fa85f3d5ce4d5a57e13eba55415b28acac5
--- 1/src/rt/rustrt.def.in
--- 2/src/rt/rustrt.def.in
+++ b/src/rt/rustrt.def.in
@@@ -17,14 -18,8 +17,11 @@@ rust_get_stder
  rust_list_dir_val
  rust_list_dir_wfd_size
  rust_list_dir_wfd_fp_buf
- rust_log_console_on
- rust_log_console_off
- rust_should_log_console
  rust_unset_sigprocmask
  rust_env_pairs
 +rust_win32_rand_acquire
 +rust_win32_rand_gen
 +rust_win32_rand_release
  upcall_rust_personality
  upcall_call_shim_on_c_stack
  upcall_call_shim_on_rust_stack