Changed ValueObject to use a dedicated ChildrenManager class to store its...

Changed ValueObject to use a dedicated ChildrenManager class to store its children, instead of an std::vector
This solves an issue where a ValueObject was getting a wrong children count (usually, a huge value) and trying to resize the vector of children to fit that many ValueObject*

Added a loop detection algorithm to the synthetic children provider for std::list

Added a few more checks to the synthetic children provider for std::vector

Both std::list and std::vector's synthetic children providers now cache the count of children instead of recomputing it every time
std::map has a field that stores the count, so there is little need to cache it on our side

llvm-svn: 152371