Subzero: Clean up a few areas.

1. Use a reverse_range() adaptor for range-based reverse iteration through containers.

2. Remove the emitting of the commented llvm-mc command line.

3. Remove a few TODOs.

4. For commented-out declarations within a class T like this:
   // T(const T&) = delete;
   // T &operator=(const T &) = delete;
Replace them with this:
   T(const T&) = default;
   T &operator=(const T &) = default;
And try to keep them private where possible.

5. Make LivenessNode and TimerTreeNode into internal classes.

BUG= none
R=jvoung@chromium.org

Review URL: https://codereview.chromium.org/830303003
diff --git a/src/IceGlobalContext.cpp b/src/IceGlobalContext.cpp
index eb312f9..0a846b9 100644
--- a/src/IceGlobalContext.cpp
+++ b/src/IceGlobalContext.cpp
@@ -130,8 +130,7 @@
                              IceString TestPrefix, const ClFlags &Flags)
     : StrDump(OsDump), StrEmit(OsEmit), VMask(Mask),
       ConstPool(new ConstantPool()), Arch(Arch), Opt(Opt),
-      TestPrefix(TestPrefix), Flags(Flags), HasEmittedFirstMethod(false),
-      RNG(""), ObjectWriter() {
+      TestPrefix(TestPrefix), Flags(Flags), RNG(""), ObjectWriter() {
   // Pre-register built-in stack names.
   if (ALLOW_DUMP) {
     newTimerStackID("Total across all functions");