Function 'printobj' in 'ltests.c' made public

It helps to have this function available for debugging.
diff --git a/ltests.c b/ltests.c
index 0513354..a4e5d28 100644
--- a/ltests.c
+++ b/ltests.c
@@ -309,6 +309,10 @@
 }
 
 
+void lua_printobj (lua_State *L, struct GCObject *o) {
+  printobj(G(L), o);
+}
+
 static int testobjref (global_State *g, GCObject *f, GCObject *t) {
   int r1 = testobjref1(g, f, t);
   if (!r1) {
diff --git a/ltests.h b/ltests.h
index 2b4498c..1a2d8d2 100644
--- a/ltests.h
+++ b/ltests.h
@@ -72,7 +72,13 @@
 /*
 ** Function to traverse and check all memory used by Lua
 */
-int lua_checkmemory (lua_State *L);
+LUAI_FUNC int lua_checkmemory (lua_State *L);
+
+/*
+** Function to print an object GC-friendly
+*/
+struct GCObject;
+LUAI_FUNC void lua_printobj (lua_State *L, struct GCObject *o);
 
 
 /* test for lock/unlock */