Revert "Work around Rust 1.12.0 bug"

This reverts commit 62604d911f09413cb1aca33d25a877b47ce736e0.
diff --git a/src/nom.rs b/src/nom.rs
index 599a4bc..d987173 100644
--- a/src/nom.rs
+++ b/src/nom.rs
@@ -232,22 +232,12 @@
     };
 }
 
-pub fn str_chars(s: &str) -> Vec<char> {
-    // Can't do `s.chars().collect()` because it triggers a compiler bug in 1.12.0
-    // https://github.com/dtolnay/syn/issues/20
-    let mut result = Vec::new();
-    for ch in s.chars() {
-        result.push(ch);
-    }
-    result
-}
-
 macro_rules! take_until {
     ($input:expr, $substr:expr) => {{
         if $substr.len() > $input.len() {
             $crate::nom::IResult::Error
         } else {
-            let substr_vec: Vec<char> = $crate::nom::str_chars($substr);
+            let substr_vec: Vec<char> = $substr.chars().collect();
             let mut window: Vec<char> = vec![];
             let mut offset = $input.len();
             let mut parsed = false;