haproxy: Update HAProxy to v2.0.0 (LTS)

- Update haproxy download URL and hash
- Add new patches
- Add several CFLAGS (derived from haproxy Makefile) to make the build work with v1.9+
- Update default configuration
- Add check-command (for config) to init-script
- Add prometheus-service from contribs by default
- Add support for uclibc to haproxy with libcrypt disabled
- Minor cleanups

I have been running v2.0 for some time now and it feels as stable as v1.8. v2.0 is the new LTS release.

Signed-off-by: Christian Lachner <gladiac@gmail.com>

net/haproxy/files/haproxy.hotplug

@@ -1,7 +1,6 @@
 #!/bin/sh
 
 if [ "$ACTION" = add ]; then
-
 	/etc/init.d/haproxy enabled && \
 		/etc/init.d/haproxy start
 fi