Fix #10671: functionConst FN with begin/end and const_iterator

[rikardfalkeborn]

Check if the iterator is assigned to a const_iterator or
const_revese_iterator, in which case it is possible the function can be
const. Unfortunately, it is not possible to remove the hard coding of
cbegin, cend, crbegin and crend due to the need to handle auto, as in
the following code snippet:

void cbegin_auto(void)
{
    for (auto it = m_str.cbegin(); it != m_str.cend(); ++it) {;}
}

[chrchr-github]

I just noticed that this has been reverted. There was a crash (reduced from http://cppcheck1.osuosl.org:8000/mp3diags) on

struct S {
  std::vector<T*> v;
  void f() const;
};
void S::f() const {
    for (std::vector<T*>::const_iterator it = v.begin(), end = v.end(); it != end; ++it)
        (*it)->g();
}

(called with inconclusive) due to not checking tokAt(-2)->variable() for NULL in

if ((var->isStlType() // assume all std::*::size() and std::*::empty() are const
                     && (Token::Match(end, "size|empty|cend|crend|cbegin|crbegin|max_size|length|count|capacity|get_allocator|c_str|str ( )") || Token::Match(end, "rfind|copy"))) ||

                    (lastVarTok->valueType() && lastVarTok->valueType()->container &&
                     ((lastVarTok->valueType()->container->getYield(end->str()) == Library::Container::Yield::START_ITERATOR) ||
                      (lastVarTok->valueType()->container->getYield(end->str()) == Library::Container::Yield::END_ITERATOR))
                     && (tok1->previous()->isComparisonOp() || (tok1->previous()->isAssignmentOp() && Token::Match(tok1->tokAt(-2)->variable()->typeEndToken(), "const_iterator|const_reverse_iterator")))))
                    ;