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.

tests/acceptance/flexnbd/constants.rb

@@ -2,6 +2,14 @@
 
 module FlexNBD
 
+  def self.binary( str )
+    if str.respond_to? :force_encoding
+      str.force_encoding "ASCII-8BIT"
+    else
+      str
+    end
+  end
+
   # eeevil is his one and only name...
   def self.read_constants
     parents = []
@@ -17,7 +25,7 @@ module FlexNBD
 
     fail "No source root!" unless source_root
 
-    headers = Dir[File.join( source_root, "src", "*.h" ) ]
+    headers = Dir[File.join( source_root, "src", "{common,proxy,server}","*.h" ) ]
 
     headers.each do |header_filename|
       txt_lines = File.readlines( header_filename )
@@ -33,8 +41,8 @@ module FlexNBD
 
   read_constants()
 
-  REQUEST_MAGIC = "\x25\x60\x95\x13" unless defined?(REQUEST_MAGIC)
-  REPLY_MAGIC = "\x67\x44\x66\x98" unless defined?(REPLY_MAGIC)
+  REQUEST_MAGIC = binary("\x25\x60\x95\x13") unless defined?(REQUEST_MAGIC)
+  REPLY_MAGIC = binary("\x67\x44\x66\x98") unless defined?(REPLY_MAGIC)
 
 end # module FlexNBD