Otherwise, groff will interpret it as a macro, causing the man page
for SDL_GetPrefPath() to be mis-rendered. Escape unescaped backslashes
as `\(rs` ("reverse solidus") before escaping other characters with
macros that, themselves, contain backslashes.
Resolves: https://github.com/libsdl-org/SDL/issues/13039
Signed-off-by: Simon McVittie <smcv@collabora.com>