dewarp1.c: fix doxygen warning + add \code cmds
dewarp1.c: fix doxygen warning + add \code cmds

The example code sections in the file comment are
wrapped in \code and \endcode, which prevents doxygen
from interpreting '&', '<' and '>' as HTML tags.

animecomico/leptonica,animecomico/leptonica,animecomico/leptonica,animecomico/leptonica,animecomico/leptonica,animecomico/leptonica