rollup merge of #22188: alexcrichton/envv2

This commit tweaks the interface of the `std::env` module to make it more
ergonomic for common usage:

* `env::var` was renamed to `env::var_os`
* `env::var_string` was renamed to `env::var`
* `env::args` was renamed to `env::args_os`
* `env::args` was re-added as a panicking iterator over string values
* `env::vars` was renamed to `env::vars_os`
* `env::vars` was re-added as a panicking iterator over string values.

This should make common usage (e.g. unicode values everywhere) more ergonomic
as well as "the default". This is also a breaking change due to the differences
of what's yielded from each of these functions, but migration should be fairly
easy as the defaults operate over `String` which is a common type to use.

[breaking-change]

2 files changed, 3 insertions, 3 deletions

diff --git a/src/libstd/rt/backtrace.rs b/src/libstd/rt/backtrace.rs
index 2af5a486d0d..ced84d7551e 100644
--- a/src/libstd/rt/backtrace.rs
+++ b/src/libstd/rt/backtrace.rs
@@ -29,7 +29,7 @@ pub fn log_enabled() -> bool {
         _ => {}
     }
 
-    let val = match env::var("RUST_BACKTRACE") {
+    let val = match env::var_os("RUST_BACKTRACE") {
         Some(..) => 2,
         None => 1,
     };
diff --git a/src/libstd/rt/util.rs b/src/libstd/rt/util.rs
index 703dca4d29b..bb57d19ed26 100644
--- a/src/libstd/rt/util.rs
+++ b/src/libstd/rt/util.rs
@@ -52,7 +52,7 @@ pub fn min_stack() -> uint {
         0 => {}
         n => return n - 1,
     }
-    let amt = env::var_string("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok());
+    let amt = env::var("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok());
     let amt = amt.unwrap_or(2 * 1024 * 1024);
     // 0 is our sentinel value, so ensure that we'll never see 0 after
     // initialization has run
@@ -63,7 +63,7 @@ pub fn min_stack() -> uint {
 /// Get's the number of scheduler threads requested by the environment
 /// either `RUST_THREADS` or `num_cpus`.
 pub fn default_sched_threads() -> uint {
-    match env::var_string("RUST_THREADS") {
+    match env::var("RUST_THREADS") {
         Ok(nstr) => {
             let opt_n: Option<uint> = nstr.parse().ok();
             match opt_n {