Add a --debug flag for DEBUG builds

If you compile with:

  DEBUG=true rake build

then all the commands get a --debug flag as an option which will make
the server dump crazy amounts of data to stderr.

src/util.c

@@ -10,6 +10,7 @@
 #include "util.h"
 
 static pthread_t main_thread;
+static int global_debug;
 
 void error_init()
 {
@@ -59,3 +60,23 @@ void* xmalloc(size_t size)
 	return p;
 }
 
+
+void set_debug(int value) {
+	global_debug = value;
+}
+
+#ifdef DEBUG
+#  include <sys/times.h>
+#  include <stdarg.h>
+
+void debug(const char *msg, ...) {
+  va_list argp;
+
+	if ( global_debug ) {
+    fprintf(stderr, "%08x %4d: ", (int) pthread_self(), (int) clock() );
+    fprintf(stderr, msg, argp);
+    fprintf(stderr, "\n");
+	}
+}
+#endif
+