Fix a bunch of spelling mistakes :\

src/zone.h

Index: src/zone.h
diff --git a/src/zone.h b/src/zone.h
index 5a8b0fedd1bf4716b62907279d89f60d3f8e7d9d..45c52a257136b3d5d5406343413ef7f9d8902d09 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -117,7 +117,7 @@ class ZoneObject {
   void* operator new(size_t size) { return Zone::New(size); }
 
   // Ideally, the delete operator should be private instead of
-  // public, but unfortuately the compiler sometimes synthesizes
+  // public, but unfortunately the compiler sometimes synthesizes
   // (unused) destructors for classes derived from ZoneObject, which
   // require the operator to be visible. MSVC requires the delete
   // operator to be public.