Split Finish into Finish and FinishImpl to have a common place to do end of
file error checking. Use that to error on an unfinished cfi_startproc.

The error is not nice, but is already better than a segmentation fault.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147717 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCObjectStreamer.cpp b/lib/MC/MCObjectStreamer.cpp
index 663d0ca..76c853c 100644
--- a/lib/MC/MCObjectStreamer.cpp
+++ b/lib/MC/MCObjectStreamer.cpp
@@ -255,7 +255,7 @@
   DF->getContents().resize(DF->getContents().size() + 4, 0);
 }
 
-void MCObjectStreamer::Finish() {
+void MCObjectStreamer::FinishImpl() {
   // Dump out the dwarf file & directory tables and line tables.
   if (getContext().hasDwarfFiles())
     MCDwarfFileTable::Emit(this);