First version of reference counting running

add: first experiment with counted references
new: n-ary operations for reference
new: more consistent reference operations
Added countedref.* to the build system
add: treating ring dependent references
Improved interface

chg: simplified redundant interface
fix: left-hand side of assignment may also be a reference
new: M-ary operations for references; def(reference)
chg: compile-time de-reference where possible
Introducing blackbox type "shared"

fix: newstruc's subexpressions working
fix: support subexpr of subexpr
chg: simplified reference dereferencing
chg: simplified shallow copies of sleftv
new: blackbox type
Treating subscriptable objects

fix: 'shared' of subscriptable types
new: reference counting rings here
chg: classes for LeftvDeep/Shallow
chg: Using class for construction
fix: got reference counts right
fix: handling unassigned references, new class for handling local identifiers
new: some comments debugging features for references and shared
Handling noninitialized and shared(ll[i])=rhs

add: replace operation for simple access of list elements
fix: handling local idroot
fix: got contexts, backreferences of indices, etc. right
fix: const qualifiers and simplified ref counting
fix: allow shared(newstr.sh)=value; assignment for non-shared rhs
chg: simplified indexed type
Nested subexpressions via shared
fix: better distingish between LeftvDeep and LeftvShallow
Fix using 'put' instead of get
new added some comments to developer's documentation, and documented system commands
chg move reusable stuff to countedref.h
Introducing weak reference for back-referenceing data

chg: more strict (added private+friend)