Processing update records (and loading a module, in general) might trigger
unexpected calls to the ASTWriter (being a mutation listener). Now we have a
mechanism to suppress those calls to the ASTWriter but notify other possible
mutation listeners.
Fixes https://llvm.org/bugs/show_bug.cgi?id=28332
Patch by Cristina Cristescu and me.
Reviewed by Richard Smith (D21800).
llvm-svn: 276473
Vassil Vassilev