Allow mixing of thread offsets between 32 and 64bit architectures.

Begin a more full implementation x86-64 REX prefixes.
Doesn't implement 64bit thread offset support for the JNI compiler.

Change-Id: If9af2f08a1833c21ddb4b4077f9b03add1a05147
diff --git a/disassembler/disassembler_mips.cc b/disassembler/disassembler_mips.cc
index 72ff761..5e89f6f 100644
--- a/disassembler/disassembler_mips.cc
+++ b/disassembler/disassembler_mips.cc
@@ -237,7 +237,7 @@
               args << StringPrintf("%+d(r%d)", offset, rs);
               if (rs == 17) {
                 args << "  ; ";
-                Thread::DumpThreadOffset(args, offset, 4);
+                Thread::DumpThreadOffset<4>(args, offset);
               }
             }
             break;