move dlclose out of dynlink.c to its own source file

src/ldso/dlclose.c

@@ -0,0 +1,9 @@
+#include <dlfcn.h>
+
+__attribute__((__visibility__("hidden")))
+int __dl_invalid_handle(void *);
+
+int dlclose(void *p)
+{
+	return __dl_invalid_handle(p);
+}

src/ldso/dynlink.c

@@ -1940,11 +1940,6 @@ int __dlinfo(void *dso, int req, void *res)
 	return 0;
 }
 
-int dlclose(void *p)
-{
-	return __dl_invalid_handle(p);
-}
-
 __attribute__((__visibility__("hidden")))
 void __dl_vseterr(const char *, va_list);