Fix reexported-modules display mangling.
Fix reexported-modules display mangling.

sep allows for horizontal separation, which is absolutely
not what we want.  Use hcat instead.  Thanks @stepcut
for reporting.

Signed-off-by: Edward Z. Yang <dbd597f5635f432486c5d365e9bb585b3eaa1853@cs.stanford.edu>

mydaum/cabal,themoritz/cabal,themoritz/cabal,themoritz/cabal,mydaum/cabal