build: downgrade EGL requirement from 1.5 to 1.4

With the previous commit, there's no need for 1.5 anymore. And in fact,
it's just too dangerous to rely on 1.5 because of all the EGL craziness.
For example, you might get a 1.5 EGL system library, but a driver might
still give you 1.4 at runtime. If you assume that you can call 1.5
functions, you will probably get random crashes in this case. What a
cursed API. (The same problem exists with EGL 1.3, but fortunately
nothing seems to use that anymore. We can just ignore that problem.)

filters/user_filters.c

@@ -93,7 +93,7 @@ const struct mp_user_filter_entry *vf_list[] = {
 #if HAVE_D3D_HWACCEL
     &vf_d3d11vpp,
 #endif
-#if HAVE_EGL_HELPERS && HAVE_GL && HAVE_EGL15
+#if HAVE_EGL_HELPERS && HAVE_GL && HAVE_EGL
     &vf_gpu,
 #endif
 };

wscript

@@ -647,17 +647,17 @@ video_output_features = [
                    check_cc(fragment=load_fragment('gl_x11.c'),
                             use=['x11', 'libdl', 'pthreads']))
     } , {
-        'name': '--egl15',
-        'desc': 'EGL 1.5',
+        'name': '--egl',
+        'desc': 'EGL 1.4',
         'groups': [ 'gl' ],
         'func': compose_checks(
             check_pkg_config('egl'),
-            check_statement(['EGL/egl.h'], 'int x[EGL_VERSION_1_5]')
+            check_statement(['EGL/egl.h'], 'int x[EGL_VERSION_1_4]')
             ),
     } , {
         'name': '--egl-x11',
         'desc': 'OpenGL X11 EGL Backend',
-        'deps': 'x11 && egl15',
+        'deps': 'x11 && egl',
         'groups': [ 'gl' ],
         'func': check_true,
     } , {

wscript_build.py

@@ -416,7 +416,7 @@ def build(ctx):
         ( "video/filter/vf_d3d11vpp.c",          "d3d-hwaccel" ),
         ( "video/filter/vf_fingerprint.c",       "zimg" ),
         ( "video/filter/vf_format.c" ),
-        ( "video/filter/vf_gpu.c",               "egl-helpers && gl && egl15" ),
+        ( "video/filter/vf_gpu.c",               "egl-helpers && gl && egl" ),
         ( "video/filter/vf_sub.c" ),
         ( "video/filter/vf_vapoursynth.c",       "vapoursynth" ),
         ( "video/filter/vf_vavpp.c",             "vaapi" ),