add: When adding a dotfile as a non-large file, mention that it's a dotfile

add: When adding a dotfile as a non-large file, mention that it's a dotfile

This is to reduce user confusion when their annex.largefiles matches it,
or is not set.

Note that, when annex.dotfiles is set, but a dotfile is not matched by
annex.largefiles, the "non-large file" message will be displayed. That
makes sense because whether the file is a dotfile does not matter with that
configuration.

Also, this slightly optimised the annex.dotfiles path in passing,
by avoiding the slight slowdown caused by the check added in commit
876d5b6c6fed7d540767783eb3d14469f41bd1c2 in that case.