ms-inline-asm: Scope inline asm labels to functions

Summary:
This fixes PR20023.  In order to implement this scoping rule, we piggy
back on the existing LabelDecl machinery, by creating LabelDecl's that
will carry the "internal" name of the inline assembly label, which we
will rewrite the asm label to.

Reviewers: rnk

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4589

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218230 91177308-0d34-0410-b5e6-96231b3b80d8
Add some documentation stating that the memory allocated by the ASTContext.h placement new does not need to be explicitly freed

Reviewers: rnk

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D5392

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@218232 91177308-0d34-0410-b5e6-96231b3b80d8