[HiTeX] Reframe do..while loops.

It's not necessary to force the default layout with tons of '@+'
commands; CWEB learned the stringent format decades ago.

Moreover, '} @+ while' adds noticeable extra whitespace.

And '@+@/' is curious, but ineffective; it always results in '@+'.

git-svn-id: svn://tug.org/texlive/trunk/Build/source@71502 c570f23f-e606-0410-a88d-b1316a301751