auto merge of #8988 : cmr/rust/fromstr_fn, r=brson

It just calls out to the associated function on the trait.

Author: bors

src/libstd/from_str.rs

@@ -19,3 +19,8 @@ pub trait FromStr {
     /// string is ill-formatted, the None is returned.
     fn from_str(s: &str) -> Option<Self>;
 }
+
+/// A utility function that just calls FromStr::from_str
+pub fn from_str<A: FromStr>(s: &str) -> Option<A> {
+    FromStr::from_str(s)
+}

src/libstd/num/float.rs

@@ -946,8 +946,8 @@ impl Float for float {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use prelude::*;
+    use super::*;
 
     use num::*;
     use num;

src/libstd/num/int_macros.rs

@@ -547,8 +547,8 @@ impl ToStrRadix for $T {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use prelude::*;
+    use super::*;
 
     use int;
     use i16;

src/libstd/num/uint_macros.rs

@@ -430,8 +430,8 @@ impl BitCount for $T {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use prelude::*;
+    use super::*;
 
     use num;
     use sys;

src/libstd/prelude.rs

@@ -41,6 +41,7 @@ pub use result::{Result, Ok, Err};
 // Reexported functions
 pub use io::{print, println};
 pub use iterator::range;
+pub use from_str::from_str;
 
 // Reexported types and traits
 pub use c_str::ToCStr;