Implement committed physical memory stats for Linux.

src/platform-solaris.cc

Index: src/platform-solaris.cc
diff --git a/src/platform-solaris.cc b/src/platform-solaris.cc
index 36d89e6d12a8c750c9cda23f5d7426adc1ef95da..16d51f19541e5bc0461c7040d434851da7f6a001 100644
--- a/src/platform-solaris.cc
+++ b/src/platform-solaris.cc
@@ -448,6 +448,12 @@ bool VirtualMemory::ReleaseRegion(void* base, size_t size) {
 }
 
 
+bool VirtualMemory::HasLazyCommits() {
+  // TODO(alph): implement for the platform.
+  return false;
+}
+
+
 class Thread::PlatformData : public Malloced {
  public:
   PlatformData() : thread_(kNoThread) {  }