REORG: include: move base64.h, errors.h and hash.h from common to to haproxy/

These ones do not depend on any other file. One used to include
haproxy/api.h but that was solely for stddef.h.
diff --git a/src/protocol.c b/src/protocol.c
index 6c4341e..3a11bdd 100644
--- a/src/protocol.c
+++ b/src/protocol.c
@@ -14,7 +14,7 @@
 #include <sys/socket.h>
 
 #include <haproxy/api.h>
-#include <common/errors.h>
+#include <haproxy/errors.h>
 #include <common/mini-clist.h>
 #include <common/standard.h>