Subzero: Add the "llvm2ice -ffunction-sections" argument.

The purpose is to enable bisection debugging of Subzero-translated functions, using objcopy to selectively splice functions from llc and Subzero into the binary.

Note that llvm-mc claims to take this argument, but actually does nothing with it, so we need to implement it in Subzero.

Also moves the ClFlags object into the GlobalContext so everyone can access it.

BUG= none
R=wala@chromium.org

Review URL: https://codereview.chromium.org/455633002

src/PNaClTranslator.cpp

diff --git a/src/PNaClTranslator.cpp b/src/PNaClTranslator.cpp
index 7f9c514..0eb6d7c 100644
--- a/src/PNaClTranslator.cpp
+++ b/src/PNaClTranslator.cpp
@@ -801,7 +801,7 @@
   return Parser.ParseThisBlock();
 }
 
-} // end of anonymous namespace.
+} // end of anonymous namespace
 
 namespace Ice {
 
@@ -856,4 +856,4 @@
   return;
 }
 
-} // end of anonymous namespace.
+} // end of namespace Ice