SuccessChanges

Summary

  1. clang/Modules: Bring back optimization lost in 31e14f41a21f (details)
Commit 8112a423a8ede9bce64b6553e6451bf10995105c by Duncan P. N. Exon Smith
clang/Modules: Bring back optimization lost in 31e14f41a21f
31e14f41a21f9016050a20f07d5da03db2e8c13e accidentally dropped caching of
failed module loads.  This brings it back by making
ModuleMap::getCachedModuleLoad return an Optional.
The file was modifiedclang/include/clang/Lex/ModuleMap.h
The file was modifiedclang/lib/Frontend/CompilerInstance.cpp