change #include "log.h" to <helper/log.h>

Changes from the flat namespace to heirarchical one.  Instead of writing:

	#include "log.h"

the following form should be used.

	#include <helper/log.h>

The exception is from .c files in the same directory.

src/server/httpd_stubs.c

@@ -21,7 +21,7 @@
 #include <config.h>
 #endif
 #include "httpd.h"
-#include "log.h"
+#include <helper/log.h>
 
 int httpd_start(struct command_context *cmd_ctx)
 {