Subzero: Enable errors for unused parameters.

Uses pragmas when including problematic LLVM headers, so that clang
doesn't warn about unused parameters -- a rampant problem in the LLVM
code.  This way, we can increase clang's pickiness on Subzero code,
and also not drown in LLVM warnings.

BUG= none
R=jpp@chromium.org, jvoung@chromium.org

Review URL: https://codereview.chromium.org/1217433002

unittest/BitcodeMunge.h

diff --git a/unittest/BitcodeMunge.h b/unittest/BitcodeMunge.h
index f257d21..3586909 100644
--- a/unittest/BitcodeMunge.h
+++ b/unittest/BitcodeMunge.h
@@ -15,7 +15,10 @@
 #ifndef SUBZERO_UNITTEST_BITCODEMUNGE_H
 #define SUBZERO_UNITTEST_BITCODEMUNGE_H
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-parameter"
 #include "llvm/Bitcode/NaCl/NaClBitcodeMunge.h"
+#pragma clang diagnostic pop
 
 #include "IceClFlags.h"