Merge branch 'Rust-Cairo' into 'master'

Cairo bindings for Rust with demo

See merge request !198

recipes/rust-cairo-demo/recipe.sh

+GIT=https://gitlab.redox-os.org/redox-os/rust-cairo-demo.git
+BUILD_DEPENDS=(cairo zlib pixman freetype libpng)
+
+function recipe_build {
+    sysroot="$(realpath ../sysroot)"
+    cp -p "$ROOT/Xargo.toml" "Xargo.toml"
+    xargo rustc --target "$TARGET" --release ${CARGOFLAGS} \
+        -- \
+        -L "${sysroot}/lib" \
+        -l cairo \
+	-l pixman-1 \
+	-l freetype \
+	-l png \
+	-l z 
+    skip=1
+}
+

recipes/rust-cairo/recipe.sh

+GIT=https://gitlab.redox-os.org/redox-os/rust-cairo.git
+BUILD_DEPENDS=(cairo zlib pixman freetype libpng)
+CARGOFLAGS="--example gui"
+
+function recipe_build {
+    sysroot="$(realpath ../sysroot)"
+    cp -p "$ROOT/Xargo.toml" "Xargo.toml"
+    xargo rustc --target "$TARGET" --release ${CARGOFLAGS} \
+        -- \
+        -L "${sysroot}/lib" \
+        -l cairo \
+	-l pixman-1 \
+	-l freetype \
+	-l png \
+	-l z 
+    skip=1
+}
+