Take the document number off and bump date.
Respond to the default string precision.

When printing char arrays, no longer count the length when
precision < 0.
Style change.

When an `if` branch is not an error/special case, explicitly use
an `else` branch instead of rely on the return flow.
Undefined fmt combos are potentially formattable.

Some flags + type hint combinations result in UB in C, so we
exclude them from internally formattable.
A C stream can not be reoriented; reopen it.
string_ref is not an issue.

If string_view is adopted, the string_view support will be there.
Add the as-if rule for potentially fmtable.
Cleanup the headers.
Better handle namespaces.
Support Boost.Format position-only syntax %N%
API as overloaded printf with iostream support.
Mention the std::printf overloading.
Use CSS to format code.
Describe the boost simple syntax.
Add changelog; date.
Add document number and revision.