REORG: include: move sample.h to haproxy/sample{,-t}.h

This one is particularly tricky to move because everyone uses it
and it depends on a lot of other types. For example it cannot include
arg-t.h and must absolutely only rely on forward declarations to avoid
dependency loops between vars -> sample_data -> arg. In order to address
this one, it would be nice to split the sample_data part out of sample.h.
diff --git a/src/map.c b/src/map.c
index 0066257..33f24dd 100644
--- a/src/map.c
+++ b/src/map.c
@@ -28,7 +28,7 @@
 #include <proto/cli.h>
 #include <proto/log.h>
 #include <proto/stream_interface.h>
-#include <proto/sample.h>
+#include <haproxy/sample.h>
 
 /* Parse an IPv4 or IPv6 address and store it into the sample.
  * The output type is IPv4 or IPv6.