Add SFML 2.x static dependency.

Includes one patch to make it compatible with Allegro 5.

sfml/Makefile

@@ -0,0 +1,43 @@
+SHELL:=/bin/bash
+
+sfml:
+	git clone https://github.com/SFML/SFML.git
+	pushd SFML && git checkout 2.5.x && patch -p1 < ../patch.txt
+	bash ../ubuntu1804.sh make impl
+	make package
+
+impl:
+	# copy & paste from allegro5
+	apt-get update
+	apt-get install -y freeglut3-dev libgl1-mesa-dev libglu1-mesa-dev mesa-common-dev \
+	                   libxcursor-dev libavfilter-dev \
+	                   libpng-dev libjpeg-dev libfreetype6-dev \
+	                   libxrandr-dev libxinerama-dev libxi-dev \
+	                   libgtk2.0-dev
+	# extra needed
+	apt-get install -y libudev-dev libopenal-dev libflac-dev libvorbis-dev
+
+	update-alternatives --install /usr/bin/c++ c++ /usr/bin/clang++-10 40
+	update-alternatives --install /usr/bin/cc cc /usr/bin/clang-10 40
+	update-alternatives --install /usr/bin/clang++ clang++ /usr/bin/clang++-10 40
+	update-alternatives --install /usr/bin/clang clang /usr/bin/clang-10 40
+	update-alternatives --install /usr/bin/ld ld /usr/bin/ld.lld-10 40
+	# static build
+	pushd SFML && \
+	cmake -DCMAKE_BUILD_TYPE=release -DCMAKE_INSTALL_PREFIX=$$PWD/sfml_static -DBUILD_SHARED_LIBS=false . && \
+	make -j $$(nproc) && \
+	make install
+
+package:
+	rm -rf out
+	mkdir -p out/opt/cppse/build/sfml/
+	cp -prv SFML/sfml_static/* out/opt/cppse/build/sfml/
+	rm -rf sfml_*_amd64.deb
+	docker run -v "$$(pwd):/src/" rayburgemeestre/fpm-ubuntu:18.04 fpm -v 1.1 -s dir -t deb -n sfml --license MPL2 --maintainer "Ray Burgemeestre <ray@cppse.nl>" --description "SFML - build dependency" --url "https://github.com/SFML/SFML.git" --deb-generate-changes -C /src/out
+
+clean:
+	rm -rf SFML
+	rm -rf out
+
+shell:
+	FLAGS="-i --privileged" bash ../ubuntu1804.sh /bin/bash

sfml/patch.txt

@@ -0,0 +1,12 @@
+diff --git a/src/SFML/Window/Unix/Display.cpp b/src/SFML/Window/Unix/Display.cpp
+index 351a1284..1019a09c 100644
+--- a/src/SFML/Window/Unix/Display.cpp
++++ b/src/SFML/Window/Unix/Display.cpp
+@@ -76,6 +76,7 @@ Display* OpenDisplay()
+ ////////////////////////////////////////////////////////////
+ void CloseDisplay(Display* display)
+ {
++    return;
+     Lock lock(mutex);
+ 
+     assert(display == sharedDisplay);