Remove -Wno-unused-parameter and -Wno-sign-promo from base cflags.

Fix associated errors about unused paramenters and implict sign conversions.
For sign conversion this was largely in the area of enums, so add ostream
operators for the effected enums and fix tools/generate-operator-out.py.
Tidy arena allocation code and arena allocated data types, rather than fixing
new and delete operators.
Remove dead code.

Change-Id: I5b433e722d2f75baacfacae4d32aef4a828bfe1b
diff --git a/runtime/dex_instruction.h b/runtime/dex_instruction.h
index 72802e4..af5d9d0 100644
--- a/runtime/dex_instruction.h
+++ b/runtime/dex_instruction.h
@@ -35,7 +35,7 @@
 class Instruction {
  public:
   // NOP-encoded switch-statement signatures.
-  enum {
+  enum Signatures {
     kPackedSwitchSignature = 0x0100,
     kSparseSwitchSignature = 0x0200,
     kArrayDataSignature = 0x0300,
@@ -79,10 +79,7 @@
     DISALLOW_COPY_AND_ASSIGN(ArrayDataPayload);
   };
 
-  // TODO: the code layout below is deliberate to avoid this enum being picked up by
-  //       generate-operator-out.py.
-  enum Code
-  {  // NOLINT(whitespace/braces)
+  enum Code {  // private marker to avoid generate-operator-out.py from processing.
 #define INSTRUCTION_ENUM(opcode, cname, p, f, r, i, a, v) cname = opcode,
 #include "dex_instruction_list.h"
     DEX_INSTRUCTION_LIST(INSTRUCTION_ENUM)