REORG: h1: merge types+proto into common/h1.h

These two files are self-contained and do not depend on other
layers, so let's remerge them together for easier manipulation.
diff --git a/src/http_htx.c b/src/http_htx.c
index 401e7f1..eb71354 100644
--- a/src/http_htx.c
+++ b/src/http_htx.c
@@ -12,10 +12,10 @@
 
 #include <common/config.h>
 #include <common/cfgparse.h>
+#include <common/h1.h>
 #include <common/http.h>
 #include <common/htx.h>
 
-#include <proto/h1.h>
 #include <proto/http_htx.h>
 
 struct buffer htx_err_chunks[HTTP_ERR_SIZE];