Fix #235: support for overriding /etc/finit.conf and /etc/finit.d

This change adds support for a new command line option finit.config=PATH
which can be used to tell Finit to start with /etc/factory.conf instead
of /etc/finit.conf.

For the complete experience a new top-level configuration file directive
`rcsd PATH` has aslo been added.  It in turn can be used by factory.conf
as follows to override /etc/finit.d:

    rcsd /etc/factory.d

Manually verified in myLinux

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

src/private.h

@@ -32,6 +32,9 @@
 #define MATCH_CMD(l, c, x) \
 	(!strncasecmp(l, c, strlen(c)) && (x = (l) + strlen(c)))
 
+extern char *finit_conf;
+extern char *finit_rcsd;
+
 extern int service_interval;
 
 int       api_init         (uev_ctx_t *ctx);