vo_opengl: fix ANGLE GLES3 mode

Turns out glGetTexLevelParameter, which is missing in ANGLE, is a
GLES3.1 function. Removing it from the list of core GLES3 functions
makes ANGLE work in GLES3 mode.

video/out/opengl/angle.c

@@ -83,7 +83,7 @@ static bool create_context_egl(MPGLContext *ctx, EGLConfig config,
     struct priv *p = ctx->priv;
 
     EGLint context_attributes[] = {
-        EGL_CONTEXT_CLIENT_VERSION, 2,
+        EGL_CONTEXT_CLIENT_VERSION, 3,
         EGL_NONE
     };
 

video/out/opengl/common.c

@@ -175,12 +175,19 @@ static const struct gl_functions gl_functions[] = {
             DEF_FN(BlitFramebuffer),
             DEF_FN(GetStringi),
             // for ES 3.0
-            DEF_FN(GetTexLevelParameteriv),
             DEF_FN(ReadBuffer),
             DEF_FN(UnmapBuffer),
             {0}
         },
     },
+    // For ES 3.1 core
+    {
+        .ver_es_core = 310,
+        .functions = (const struct gl_function[]) {
+            DEF_FN(GetTexLevelParameteriv),
+            {0}
+        },
+    },
     // Useful for ES 2.0
     {
         .ver_core = 110,