Extended precision floating point support

Created by: chuckatkins

This is to track the issues surrounding support for extended precision float, i.e. long double. Some things to consider:

1. The multitude of precision and byte representations to support.
2. Cross-language support (Fortran REAL(16) may or may not be supported at all and if it is, may not be the same as the corresponding C / C++ long double)
3. Padding issues on non-dense representations (i.e. 80-bit long double taking up 128 bits of space)
4. Read support for formats not supported by the current architecture.