Deprecate str::from_chars

Use `String::from_chars` instead

[breaking-change]

src/libregex/parse.rs

@@ -510,7 +510,7 @@ impl<'a> Parser<'a> {
             };
         self.chari = closer;
         let greed = try!(self.get_next_greedy());
-        let inner = str::from_chars(
+        let inner = String::from_chars(
             self.chars.as_slice().slice(start + 1, closer));
 
         // Parse the min and max values from the regex.
@@ -944,7 +944,7 @@ impl<'a> Parser<'a> {
     }
 
     fn slice(&self, start: uint, end: uint) -> String {
-        str::from_chars(self.chars.as_slice().slice(start, end)).to_string()
+        String::from_chars(self.chars.as_slice().slice(start, end))
     }
 }