Revert a C API difference that I incorrectly introduced.

LLVMGetBitcodeModuleInContext should not take ownership on error. I will
try to localize this odd api requirement, but this should get the bots green.

llvm-svn: 211213
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.h b/llvm/lib/Bitcode/Reader/BitcodeReader.h
index 51a8c6a..6aa3e0e5 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.h
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.h
@@ -239,6 +239,10 @@
 
   void FreeState();
 
+  void releaseBuffer() {
+    Buffer = nullptr;
+  }
+
   bool isMaterializable(const GlobalValue *GV) const override;
   bool isDematerializable(const GlobalValue *GV) const override;
   std::error_code Materialize(GlobalValue *GV) override;