simply set a hardcoded recursion limit to 2000 (inspired by Python's)
to avoid infinitely recursing into arbitrary data structures
assert() the depth. unsure if this is the right approach, but given
that HandleNode() is "void", I am not sure how else to return an
error. the problem with this approach of course is that it will still
crash the caller, unless they have proper exception handling in place.
Closes: #459
* Add compilation flags: -Wshadow -Weffc++ -pedantic -pedantic-errors
* Delete implicit copy & move constructors & assignment operators
in classes with pointer data members.
* An exception to the above: Add default copy & move constructors &
assignment operators for the Binary class.
* Convert boolean RegEx operators to binary operators.
* Initialize all members in all classes in ctors.
* Let default ctor delegate to the converting ctor in
Binary and RegEx
* Don't change any tests except regex_test (as a result of the change
to binary operators).
Note: https://bugzilla.redhat.com/show_bug.cgi?id=1544675 makes
-Weffc++ report a false positive in "include/yaml-cpp/node/impl.h".
