pidgin/pidgin

Fix an issue where color_is_visible was incorrectly comparing unsigned values that were potentially wrapping.

Testing Done:
Compile only.

Reviewed at https://reviews.imfreedom.org/r/493/
FROM pidgin/release-builder:release-2.x.y AS build
COPY . /pidgin
RUN set -ex && \
cd /pidgin && \
./autogen.sh --enable-debug && \
make -s -j$(nproc) docs
FROM rwgrim/goserve
EXPOSE 3000
COPY --from=build /pidgin/doc/html html