Switch from a rake-based build to a make-based build.

This commit beefs up the Makefile to do the build, instead of the
Rakefile.

It also removes from the Rakefile the dependency on rake_utils, which
should mean it's ok to build in a schroot.

The files are reorganised to make the Makefile rules more tractable,
although the reorganisation reveals a problem with our current code
organisation.

The problem is that the proxy-specific code transitively depends on the
server code via flexnbd.h, which has a circular dependency on the server
and client structs. This should be broken in a future commit by
separating the flexnbd struct into a shared config struct and
server-specific parts, so that the server code can be moved into
src/server to more accurately show the functional dependencies.

src/common/parse.h

@@ -0,0 +1,29 @@
+#ifndef PARSE_H
+#define PARSE_H
+
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include <arpa/inet.h>
+#include <unistd.h>
+
+union mysockaddr {
+	unsigned short      family;
+	struct sockaddr     generic;
+        struct sockaddr_in  v4;
+        struct sockaddr_in6 v6;
+        struct sockaddr_un  un;
+};
+
+struct ip_and_mask {
+	union mysockaddr ip;
+	int              mask;
+};
+
+int parse_ip_to_sockaddr(struct sockaddr* out, char* src);
+int parse_to_sockaddr(struct sockaddr* out, char* src);
+int parse_acl(struct ip_and_mask (**out)[], int max, char **entries);
+void parse_port( char *s_port, struct sockaddr_in *out );
+
+#endif
+