Subzero: Use a common RelocOffsetType / RelocOffsetT.

There is one in IceDefs.h and one in IceGlobalInits.h. Can we just use one?

BUG=none (mini cleanup)
R=kschimpf@google.com, stichnot@chromium.org

Review URL: https://codereview.chromium.org/695563006

src/IceDefs.h

diff --git a/src/IceDefs.h b/src/IceDefs.h
index 0beb3a3..2f0547e 100644
--- a/src/IceDefs.h
+++ b/src/IceDefs.h
@@ -85,6 +85,7 @@
 
 // PNaCl is ILP32, so theoretically we should only need 32-bit offsets.
 typedef int32_t RelocOffsetT;
+enum { RelocAddrSize = 4 };
 
 enum LivenessMode {
   // Basic version of live-range-end calculation.  Marks the last uses