Modernize code base to C++11 (first)

[fangism]

In its current state, the code base compiles using the C++98 standard. It is year 2025 soon. It struggles to compile with most reasonably recent compilers. Modernization will need to be done in phases, rather than jumping to c++20 or c++23 all at once.

Phase 1: compile against -std=c++11 before we jump to c++14, c++17, etc. c++11 was a "great leap forward", and this transition is expected to be laborious. Changes to this effect will happen on the remove-STL-fwd branch.

Some suggested configuration options for testing:
configure CC="clang-16" CXX="clang++-16" CXXFLAGS='CXXFLAGS=-g -O2 -std=c++11 -Wno-unused-local-typedef'

[fangism]

Notes: std::binary_function and std::unary_function were marked deprecated in C++11, with the introduction of lambdas. Conditioning the code to work both pre- and post-c++11 is quite possibly more effort than it is worth. We are going to rely heavily on the unit-tests and integration-tests to prevent breakage in this transition.

[fangism]

Related <functional>-code in hackt's code base:

• util/compose.hh for unary_compose and binary_compose. Replace these with lambdas.
• util/deference.hh for dereference. Can be replaced with lambdas.
• many uses of std::mem_fun_ref, to be replaced by std::mem_fn. Replaceable with lambdas.
• std::bind2nd and std::bind1st to be replaced by std::bind, or just lambdas with captures.

Pointer management:

• replace excl_ptr withstd::unique_ptr and replace count_ptr with std::shared_ptr. These are not perfect drop-in replacements, some additional work is expected around object serialization persistent_object_manager.

(just to name a few)