Debug Info: generate a unique identifier for C++ struct, class, union, and enum.

We use CXX mangler to generate unique identifier for external C++ struct,
union, class and enum. Types with unique identifier are added to retained
types by DIBuilder.

Testing cases are updated to reflect the unique identifier generated for types.
The order of MDNodes is changed because of retained types and testing cases
are updated accordingly.

Testing case debug-info-uuid.cpp now emits error with Itanium mangler, since
uuid is not yet handled in Itanium mangler. And it will check for the error
message.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189622 91177308-0d34-0410-b5e6-96231b3b80d8
Adjust clang for change to APFloat::toString.

I changed the diagnostic printing code because it's probably better
to cut off a digit from DBL_MAX than to print something like
1.300000001 when the user wrote 1.3.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189625 91177308-0d34-0410-b5e6-96231b3b80d8