Remove old checks for dlfcn.h and sys/dl.h

configure.ac

@@ -713,7 +713,6 @@ fi
 # Only test for dlopen() if the others didn't work
 LIBDL=""
 if test "${ac_cv_have_plugins}" = "no" -o "${SYS}" = "darwin"; then
-  AC_CHECK_HEADERS(dlfcn.h sys/dl.h)
   ac_cv_my_have_dlopen=no
   AC_CHECK_FUNC(dlopen, [
     ac_cv_my_have_dlopen=yes

modules/codec/realvideo.c

@@ -45,13 +45,8 @@ int WINAPI FreeLibrary( void *handle );
 #   define WINAPI
 #endif
 
-#if defined(HAVE_DL_DLOPEN)
-#   if defined(HAVE_DLFCN_H) /* Linux, BSD, Hurd */
-#       include <dlfcn.h>
-#   endif
-#   if defined(HAVE_SYS_DL_H)
-#       include <sys/dl.h>
-#   endif
+#ifndef WIN32
+#   include <dlfcn.h>
 #endif
 
 typedef struct cmsg_data_s