BUILD: idleconns: include missing ebmbtree.h at several places

backend.c, all muxes, backend.c started manipulating ebmb_nodes with
the introduction of idle conns but the types were inherited through
other includes. Let's add ebmbtree.h there.

src/backend.c

@@ -19,6 +19,8 @@
 #include <ctype.h>
 #include <sys/types.h>
 
+#include <import/ebmbtree.h>
+
 #include <haproxy/acl.h>
 #include <haproxy/api.h>
 #include <haproxy/arg.h>

src/hlua_fcn.c

@@ -21,6 +21,8 @@
 #include <lua.h>
 #include <lualib.h>
 
+#include <import/ebmbtree.h>
+
 #include <haproxy/cli-t.h>
 #include <haproxy/errors.h>
 #include <haproxy/hlua-t.h>

src/mux_fcgi.c

@@ -11,6 +11,8 @@
  */
 
 #include <import/ist.h>
+#include <import/eb32tree.h>
+#include <import/ebmbtree.h>
 
 #include <haproxy/api.h>
 #include <haproxy/cfgparse.h>

src/mux_h1.c

@@ -10,6 +10,7 @@
  *
  */
 #include <import/ebistree.h>
+#include <import/ebmbtree.h>
 
 #include <haproxy/api.h>
 #include <haproxy/cfgparse.h>

src/mux_h2.c

@@ -11,6 +11,7 @@
  */
 
 #include <import/eb32tree.h>
+#include <import/ebmbtree.h>
 #include <haproxy/api.h>
 #include <haproxy/cfgparse.h>
 #include <haproxy/connection.h>