Make ObjectFile and BitcodeReader always own the MemoryBuffer.

This allows us to just use a std::unique_ptr to store the pointer to the buffer.
The flip side is that they have to support releasing the buffer back to the
caller.

Overall this looks like a more efficient and less brittle api.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211542 91177308-0d34-0410-b5e6-96231b3b80d8

lib/IR/Module.cpp

@@ -400,10 +400,13 @@ std::error_code Module::materializeAll() {
   return Materializer->MaterializeModule(this);
 }
 
-std::error_code Module::materializeAllPermanently() {
+std::error_code Module::materializeAllPermanently(bool ReleaseBuffer) {
   if (std::error_code EC = materializeAll())
     return EC;
 
+  if (ReleaseBuffer)
+    Materializer->releaseBuffer();
+
   Materializer.reset();
   return std::error_code();
 }