Restructure release notes.
Restructure release notes.

Differential revision: https://reviews.llvm.org/D22605


git-svn-id: a34e9779ed74578ad5922b3306b3d80a0c825546@276371 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra,llvm-mirror/clang-tools-extra