HowToReleaseLLVM: Add information about dot releases

Based on the following discussion:
http://llvm.1065342.n5.nabble.com/LLVM-3-4-stable-releases-td65005.html

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200772 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed