Record correct source range for defaulted/deleted members.

Fixes https://llvm.org/bugs/show_bug.cgi?id=20744

struct A {

A() = default;
};

Previously the source range of the declaration of A ended at the ')'. It should
include the '= default' part as well. The same for '= delete'.

Note: this will break one of the clang-tidy fixers, which is going to be
addessed in a follow-up patch.

Differential Revision: http://reviews.llvm.org/D8465

llvm-svn: 233028