migrate fully to meson build system

- drop old build system
- move shared include and source files to common directory
- drop "rc-" prefix from shared include and source files
- move executable-specific code to individual directories under src
- adjust top-level .gitignore file for new build system

This closes #489.

support/init.d.examples/.gitignore

@@ -1,11 +0,0 @@
-avahi-dnsconfd
-avahid
-dhcpcd
-dbus
-hald
-named
-ntpd
-openvpn
-polkitd
-sshd
-wpa_supplicant

support/init.d.examples/Makefile

@@ -1,11 +0,0 @@
-DIR=	${DATADIR}/support/init.d.examples
-INC=	README.md
-SRCS=	avahi-dnsconfd.in avahid.in dhcpcd.in dbus.in \
-	hald.in named.in ntpd.in \
-	openvpn.in polkitd.in sshd.in wpa_supplicant.in
-BIN=	${OBJS}
-
-MK=	../../mk
-
-include ${MK}/os.mk
-include ${MK}/scripts.mk