libsystemd: new library, refactor sd-daemon.[ch] test code

This commit introduces a bare-bones replacement for libsystemd:

 - Build .so file and add --with-libsystemd to configure
 - Add capabilities support to test/src/serv.c
 - Update tests to account for a Finit built w/o libsystemd support

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

libsystemd/Makefile.am

@@ -0,0 +1,12 @@
+# libsystemd replacement library
+lib_LTLIBRARIES          = libsystemd.la
+libsystemd_la_SOURCES    = sd-daemon.c sd-daemon.h
+libsystemd_la_LDFLAGS    = -version-info 0:0:0
+
+# pkg-config support
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = libsystemd.pc
+
+# Install header to systemd/ subdirectory
+systemddir = $(includedir)/systemd
+systemd_HEADERS = sd-daemon.h