Fix some overflow errors

Author: alexcrichton

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 
 name = "glob"
-version = "0.2.1"
+version = "0.2.2"
 authors = ["The Rust Project Developers"]
 license = "MIT/Apache-2.0"
 homepage = "https://github.com/rust-lang/glob"

src/lib.rs

@@ -497,7 +497,7 @@ impl Pattern {
                 }
                 '[' => {
 
-                    if i <= chars.len() - 4 && chars[i + 1] == '!' {
+                    if i + 4 <= chars.len() && chars[i + 1] == '!' {
                         match chars[i + 3..].position_elem(&']') {
                             None => (),
                             Some(j) => {
@@ -508,7 +508,7 @@ impl Pattern {
                                 continue;
                             }
                         }
-                    } else if i <= chars.len() - 3 && chars[i + 1] != '!' {
+                    } else if i + 3 <= chars.len() && chars[i + 1] != '!' {
                         match chars[i + 2..].position_elem(&']') {
                             None => (),
                             Some(j) => {