[Parser] Avoid spurious 'missing template' error in presence of typos.

Suppress those diagnostics if lhs of a member expression contains
errors. Typo correction produces dependent expressions even in
non-template code, that led to spurious diagnostics before.

previous:
    /tmp/t.cpp:6:17: error: use 'template' keyword to treat 'f' as a dependent template name
    auto a = bilder.f<int>();
                    ^
                    template
    /tmp/t.cpp:6:10: error: use of undeclared identifier 'bilder'; did you mean 'builder'?
    auto a = bilder.f<int>();
             ^~~~~~
             builder

vs now:

    /tmp/t.cpp:6:10: error: use of undeclared identifier 'bilder'; did you mean 'builder'?
    auto a = bilder.f<int>();
             ^~~~~~
             builder

Original patch from Ilya.

Reviewers: sammccall

Reviewed By: sammccall

Tags: #clang

Differential Revision: https://reviews.llvm.org/D65592