support "variable may not be initialized on some execution path" in
_for, _while
support "variable may not be initialized on some execution path" in _try
refactoring(): added s:push_varstack()
fixed bug in restore_varstack()
refactoring(): call simpl_varstack() in restore_varstack()
refactoring(): upd debug messages
fixed bug in restore_varstack()
fixed bug in compile_body: invalid "unreachable code"
fixed bug in _try
fixed bug in _try