Upgrade to OpenGL ES 3.2 (#1879)

* upgrade to opengl 3.2

* cornerpin: no need for hack

* renderer: Update OCIO shader language to ES 3.0

Co-authored-by: Thomas Wilshaw <thomaswilshaw@gmail.com>

app/shaders/rgbwaveform.frag

@@ -5,7 +5,8 @@ uniform vec3 luma_coeffs;
 
 uniform float waveform_scale;
 
-varying vec2 ove_texcoord;
+in vec2 ove_texcoord;
+out vec4 frag_color;
 
 void main(void) {
     float waveform_height = ceil(waveform_scale * viewport.y);
@@ -33,5 +34,5 @@ void main(void) {
     }
 
     col.rgb += vec3(col.w);
-    gl_FragColor = vec4(col.rgb, 1.0);
+    frag_color = vec4(col.rgb, 1.0);
 }