avfilter/frei0r: use win32dlfcn wrapper

configure

@@ -3597,8 +3597,9 @@ firequalizer_filter_select="rdft"
 flite_filter_deps="libflite"
 framerate_filter_select="scene_sad"
 freezedetect_filter_select="scene_sad"
-frei0r_filter_deps="frei0r libdl"
-frei0r_src_filter_deps="frei0r libdl"
+frei0r_deps_any="libdl LoadLibrary"
+frei0r_filter_deps="frei0r"
+frei0r_src_filter_deps="frei0r"
 fspp_filter_deps="gpl"
 histeq_filter_deps="gpl"
 hqdn3d_filter_deps="gpl"
@@ -6383,7 +6384,7 @@ enabled cuda_nvcc         && { check_nvcc cuda_nvcc || die "ERROR: failed checki
 enabled chromaprint       && require chromaprint chromaprint.h chromaprint_get_version -lchromaprint
 enabled decklink          && { require_headers DeckLinkAPI.h &&
                                { test_cpp_condition DeckLinkAPIVersion.h "BLACKMAGIC_DECKLINK_API_VERSION >= 0x0a0b0000" || die "ERROR: Decklink API version must be >= 10.11"; } }
-enabled frei0r            && require_headers "frei0r.h dlfcn.h"
+enabled frei0r            && require_headers "frei0r.h"
 enabled gmp               && require gmp gmp.h mpz_export -lgmp
 enabled gnutls            && require_pkg_config gnutls gnutls gnutls/gnutls.h gnutls_global_init
 enabled jni               && { [ $target_os = "android" ] && check_headers jni.h && enabled pthreads || die "ERROR: jni not found"; }

libavfilter/vf_frei0r.c

@@ -22,12 +22,12 @@
  * frei0r wrapper
  */
 
-#include <dlfcn.h>
 #include <frei0r.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include "config.h"
+#include "compat/w32dlfcn.h"
 #include "libavutil/avstring.h"
 #include "libavutil/common.h"
 #include "libavutil/eval.h"