Throwing exception on NULL is a bit extreme, and unhelpful when it
happens in rarely-tested error paths. Printing "(null)" is safer and
provides compatibility with glibc sprintf.
This was SVN commit r16180.
These cause a lot of type-safety trouble - unsupported types passed into
fmt::sprintf (like CStr or enums) will be accepted at compile time, but
trigger an exception at runtime. Remove them, so we'll get either an
implicit conversion to a supported type, or a compile-time error.
This was SVN commit r16179.
