cxxomfort: Sequence Helpers

cxxomfort rel.20210622

Simple backports for C++ - http://ryan.gulix.cl/fossil.cgi/cxxomfort/

Interfaces defined in this file:

is_std_array
is_sequence_container
is_indexable_like_array
is_iterator
make_array (to be moved to <array>
seq_ , generic_sequence_t

Pending:

array<> in C++03 mode with NO_TR1 defined