When we notice that a member function is defined with "= delete" or "=

default", make a note of which is used when creating the
initial declaration. Previously, we would wait until later to handle
default/delete as a definition, but this is too late: when adding the
declaration, we already treated the declaration as "user-provided"
when in fact it was merely "user-declared".

Fixes PR10861 and PR10442, along with a bunch of FIXMEs.

llvm-svn: 144011