convert: fix line ending of mapfile and commit.desc file
Follows up 42a393ea56d2. CRLF vs LF doesn't really matter as we do strip()
or rstrip() on read, but mixing them isn't nice. So let's restore the old
I don't know whether CVS/Root, CVS/Repository, and ~/.cvspass are written
in native line ending, so I leave them read as binary files.