Factor out exception specification information from
FunctionProtoType::ExtProtoInfo. Most of the users of these fields don't care
about the other ExtProtoInfo bits and just want to talk about the exception
specification.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@214450 91177308-0d34-0410-b5e6-96231b3b80d8