[PATCH] Allow return type deduction for templates in delayed parsing mode.

[Reid Kleckner]

  Are you sure this is an MSVC-compatible change?  MSVC allows late specified return types, and does so while delaying the parsing of the body.  Consider this test case, which cl accepts and clang -fno-delayed-template-parsing rejects:

    extern "C" int puts(const char *s);
    template <typename T>
    auto foo(T x) -> decltype(x) {
      ::bar();
      return x;
    }
    void bar() { puts("bar"); }
    int main() { return foo(0); }

http://llvm-reviews.chandlerc.com/D2053