[PCH] When chaining a PCH and serializing HeaderSearch, make sure the HeaderFileInfos
from the primary PCH is deserialized, otherwise we lose info that headers were
already #imported/#included.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@144510 91177308-0d34-0410-b5e6-96231b3b80d8
7 files changed