Simplify MacroInfo lifetime management. We don't need three different functions
to destroy one of these.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213837 91177308-0d34-0410-b5e6-96231b3b80d8
[modules] Slightly expand module semantics documentation.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@213838 91177308-0d34-0410-b5e6-96231b3b80d8