ots-side-by-side.1: escape ascii-art sections

[gagath]

This patch fixes the warnings for the following command:

LC_ALL=C.UTF-8 MANROFFSEQ='' MANWIDTH=80 \
    man --warnings -E UTF-8 -l -Tutf8 -Z <file> >/dev/null

Warnings fixed:

42: '\ ' is not allowed in a name
93: warning: macro '#*' not defined
101: '\ ' is not allowed in a name
135: '\ ' is not allowed in a name
135: warning: macro '#+' not defined
42: warning: macro '###+.#.' not defined
61: '\ ' is not allowed in a name
61: warning: macro '##' not defined
62: '\ ' is not allowed in a name
63: '\ ' is not allowed in a name
84: '\ ' is not allowed in a name
84: warning: macro '##+.#+' not defined
93: '\ ' is not allowed in a name

[khaledhosny]

Thanks!