[flang] Drill down to a working implementation of the APIs for an

internal formatted WRITE with no data list items.

Improve argument names in io-api.h

Bump up error number to not conflict with errno values

Use Fortran::runtime::io namespace

Add wrapper around malloc/free, allow use of unique_ptr with wrapper

IoErrorHandler

Revamp FormatContext, use virtual member functions

Update comment syntax, allow for old C

12HHELLO, WORLD

Remove files not yet ready for review

Use std::forward

Fix gcc build warnings

Fix redundant filename in license boilerplate

Reduce runtime dependence on compiler binary libraries, fixing shared lib builds

Original-commit: flang-compiler/f18@839a91f1d699cd839767407bcdb1e384f2d2b730
Reviewed-on: https://github.com/flang-compiler/f18/pull/946