MINOR: stats: export function to allocate extra proxy counters

Remove static qualifier on stats_allocate_proxy_counters_internal. This
function will be used to allocate extra counters at runtime for dynamic
servers.
diff --git a/include/haproxy/stats.h b/include/haproxy/stats.h
index cbc33f2..a97740d 100644
--- a/include/haproxy/stats.h
+++ b/include/haproxy/stats.h
@@ -126,6 +126,8 @@
 #define MK_STATS_PROXY_DOMAIN(px_cap) \
 	((px_cap) << STATS_PX_CAP | STATS_DOMAIN_PROXY)
 
+int stats_allocate_proxy_counters_internal(struct extra_counters **counters,
+                                           int type, int px_cap);
 int stats_allocate_proxy_counters(struct proxy *px);
 
 void stats_register_module(struct stats_module *m);
diff --git a/src/stats.c b/src/stats.c
index 67d85a7..e54d13a 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -4859,8 +4859,8 @@
 	return stats_dump_json_schema_to_buffer(appctx->owner);
 }
 
-static int stats_allocate_proxy_counters_internal(struct extra_counters **counters,
-                                                  int type, int px_cap)
+int stats_allocate_proxy_counters_internal(struct extra_counters **counters,
+                                           int type, int px_cap)
 {
 	struct stats_module *mod;