Always mark friend function declarations in class templates as
implicitly instantiable, even if we don't see a body on the friend
function declaration. The body may simply have not yet been attached.
This fixes PR10666.

There may be an alternate, preferred implementation strategy, see my
FIXME. Review would definitely be appreciated Doug. =D

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@137934 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed