Un-revert r196358: "llvm-cov: Added support for function checksums."

And add the proper fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196367 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/GCOV.h

@@ -250,6 +250,7 @@ public:
 private:
   GCOVFile &Parent;
   uint32_t Ident;
+  uint32_t Checksum;
   uint32_t LineNumber;
   StringRef Name;
   StringRef Filename;