Merge branch 'master' into deterministic-zlib-settings

Cargo.toml

@@ -70,3 +70,5 @@ name = "oxipng"
 path = "src/lib.rs"
 [profile.dev]
 opt-level = 2
+[profile.release]
+lto = true

tests/regression.rs

@@ -600,6 +600,7 @@ fn issue_159() {
 }
 
 #[test]
+#[cfg(target_pointer_width = "64")]
 fn issue_167() {
     test_it_converts(
         "tests/files/issue-167.png",
@@ -610,3 +611,15 @@ fn issue_167() {
         BitDepth::Eight,
     );
 }
+
+#[test]
+fn issue_171() {
+    test_it_converts(
+        "tests/files/issue-171.png",
+        None,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+    );
+}