Allow platforms (linux and win32) to not force 16-byte alignment...

src/platform-macos.cc

Index: src/platform-macos.cc
===================================================================
--- src/platform-macos.cc	(revision 358)
+++ src/platform-macos.cc	(working copy)
@@ -300,9 +300,18 @@
 }
 
 
-double OS::nan_value() { return NAN; }
+double OS::nan_value() {
+  return NAN;
+}
 
 
+int OS::ActivationFrameAlignment() {
+  // OS X activation frames must be 16 byte-aligned; see "Mac OS X ABI
+  // Function Call Guide".
+  return 16;
+}
+
+
 int OS::StackWalk(StackFrame* frames, int frames_size) {
 #ifndef MAC_OS_X_VERSION_10_5
   return 0;