contrib: add xcb and update it

contrib/src/xcb/SHA512SUMS

+d48cbd2a738ee8cc57fad954360fde8ccff3b9a2bf6bfa56459197b7b965f2b94ccd863dbbb6917e80ff3f324f41938e5745f2fa4a2168659fa4b96df23f7ded  libxcb-1.7.tar.bz2

contrib/src/xcb/rules.mak

+# X protocol C language Bindings
+
+XCB_VERSION := 1.7
+XCB_URL := http://xcb.freedesktop.org/dist/libxcb-$(XCB_VERSION).tar.bz2
+
+$(TARBALLS)/libxcb-$(XCB_VERSION).tar.bz2:
+	$(call download,$(XCB_URL))
+
+.sum-xcb: libxcb-$(XCB_VERSION).tar.bz2
+
+libxcb: libxcb-$(XCB_VERSION).tar.bz2 .sum-xcb
+	$(UNPACK)
+	$(MOVE)
+
+XCBCONF := \
+	--enable-composite \
+	--disable-damage \
+	--disable-dpms \
+	--disable-dri2 \
+	--disable-glx \
+	--enable-randr \
+	--disable-render \
+	--disable-resource \
+	--disable-screensaver \
+	--disable-shape \
+	--enable-shm \
+	--disable-sync \
+	--disable-xevie \
+	--disable-xfixes \
+	--disable-xfree86-dri \
+	--disable-xinerama \
+	--disable-xinput \
+	--disable-xprint \
+	--disable-selinux \
+	--disable-xtest \
+	--enable-xv \
+	--disable-xvmc \
+	$(HOSTCONF)
+
+.xcb: libxcb
+	cd $< && $(HOSTVARS) ./configure $(XCBCONF)
+	cd $< && $(MAKE) install
+	touch $@