Check whether a pending instantiation needs to be instantiated (or whether an instantiation already exists).
Verify the size of the PendingInstantiations record (was only checking size of existing PendingInstantiations).
Migrate Obj-C++ part of redecl-merge into separate test, now that this is growing.
templates.mm: test that CodeGen has seen exactly one definition of template instantiations.
redecl-merge.m: use "@" specifier for expected-diagnostics.
llvm-svn: 164993