Implement committed physical memory stats for Linux.

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index b39dfc0eef8aa6132fee8de5ab519d03dcabcb98..e35df11a7c7bdfc8a8d754c570db22632b9b74e9 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -359,6 +359,12 @@ bool VirtualMemory::Guard(void* address) {
 }
 
 
+bool VirtualMemory::HasLazyCommits() {
+  // TODO(alph): implement for the platform.
+  return false;
+}
+
+
 class Thread::PlatformData : public Malloced {
  public:
   PlatformData() : thread_(kNoThread) {}