`#ifdef` and `#ifndef` directives missing from `ifCond`

[ludviggunne]

Failing test:

    {
        const char code[] = "#ifdef NOTDEFINED\n"
                            "#endif\n"
                            "#ifndef NOTDEFINED\n"
                            "#endif\n";
        std::list<simplecpp::IfCond> ifCond;
        ASSERT_EQUALS("", preprocess(code, &ifCond));
        ASSERT_EQUALS(2, ifCond.size());
        auto it = ifCond.cbegin();
        ASSERT_EQUALS(0, it->location.fileIndex);
        ASSERT_EQUALS(1, it->location.line);
        ASSERT_EQUALS(2, it->location.col);
        ASSERT_EQUALS("defined(NOTDEFINED)", it->E);
        ASSERT_EQUALS(0, it->result);
        ++it;
        ASSERT_EQUALS(0, it->location.fileIndex);
        ASSERT_EQUALS(3, it->location.line);
        ASSERT_EQUALS(2, it->location.col);
        ASSERT_EQUALS("!defined(NOTDEFINED)", it->E);
        ASSERT_EQUALS(1, it->result);
    }