CLEANUP: includes: fix includes for a number of users of fd.h

It appears that fd.h includes a number of unneeded files and was
included from standard.h, and as such served as an intermediary
to provide almost everything to everyone.

By removing its useless includes, a long dependency chain broke
but could easily be fixed.

src/sample.c

@@ -13,6 +13,7 @@
 
 #include <string.h>
 #include <arpa/inet.h>
+#include <stdio.h>
 
 #include <common/chunk.h>
 #include <common/standard.h>