data/crc32: generation cleanups.
type_traits: rework size-based type selection.

Whenever possible I'm trying to use C++11-style template aliases,
rather than the C++03-style "::type" members.  It keeps clients from
repeating the word 'typename' like a mantra.

It appears that I have no uses of these templates in my codebase, ever
since I started letting the compiler determine integer widths.  So this
is a great opportunity to fix their shape.
type_traits: add *minimum* size selection.
biffield: breaking change in definition macro.

The filename passed as ETL_BFF_DEFINITION_FILE must now be quoted,
largely as a concession to formatting tools that want to introduce
spaces if it isn't.  This winds up being *less* complex and I'm not
sure why I didn't do it from the beginning.
Remove legacy Makefiles.

I had left these in as documentation for people who didn't want to
study Cobble, but in practice, they're written in a very unusual
dialect of Make that probably won't help.
Fixes for Clang compilation.

Mostly C++14 compatibility fixes, but there was also an explicit
conversion being invoked in Maybe...implicitly.  Unclear why GCC
was cool with that.