Enable emission of debugger-friendly bitcode

- Add "-g" flag to llvm-rs-cc in order to emit debug metadata
- Add optimization level parameter -O and tests
- Add lit based tests (use llvm-lit from libbcc/tests/debuginfo)
-- Add README file for lit-tests directory

Change-Id: I5e2f6f9b6f536fa7a10de008b54ac0878cf352a9
diff --git a/slang_backend.cpp b/slang_backend.cpp
index 29ad353..7809a77 100644
--- a/slang_backend.cpp
+++ b/slang_backend.cpp
@@ -204,7 +204,6 @@
                  llvm::raw_ostream *OS,
                  Slang::OutputType OT)
     : ASTConsumer(),
-      mCodeGenOpts(CodeGenOpts),
       mTargetOpts(TargetOpts),
       mpModule(NULL),
       mpOS(OS),
@@ -215,6 +214,7 @@
       mCodeGenPasses(NULL),
       mLLVMContext(llvm::getGlobalContext()),
       mDiagEngine(*DiagEngine),
+      mCodeGenOpts(CodeGenOpts),
       mPragmas(Pragmas) {
   FormattedOutStream.setStream(*mpOS,
                                llvm::formatted_raw_ostream::PRESERVE_STREAM);