[CLEANUP] remove many #include <types/xxx> from C files

It should be stated as a rule that a C file should never
include types/xxx.h when proto/xxx.h exists, as it gives
less exposure to declaration conflicts (one of which was
caught and fixed here) and it complicates the file headers
for nothing.

Only types/global.h, types/capture.h and types/polling.h
have been found to be valid includes from C files.
diff --git a/src/appsession.c b/src/appsession.c
index 10b4df0..b3f2c76 100644
--- a/src/appsession.c
+++ b/src/appsession.c
@@ -21,11 +21,9 @@
 #include <common/ticks.h>
 #include <common/time.h>
 
-#include <types/buffers.h>
 #include <types/global.h>
-#include <types/proxy.h>
-#include <types/server.h>
 
+#include <proto/proxy.h>
 #include <proto/task.h>
 
 static struct task *appsess_refresh = NULL;