GraphEdit Handle Drawing: Fix handle-vertex size regression (2.7 -> 2.8)

Keyframe handle vertices (the circles on the ends of the handles)
should always be larger than the central vertex. This brings back the
"outer" radius value from the old gluDisk(), and doubles it to get the
necessary diameter, to scale it properly.

TODO's:
- Get rid of all fills inside these circles
- Make the central vertex square-shaped again

source/blender/editors/space_graph/graph_draw.c

@@ -259,7 +259,7 @@ static void draw_fcurve_handle_vertices(FCurve *fcu, View2D *v2d, bool sel_handl
 	immBindBuiltinProgram(GPU_SHADER_2D_POINT_UNIFORM_SIZE_UNIFORM_COLOR_OUTLINE_AA);
 
 	/* set handle size */
-	immUniform1f("size", (UI_GetThemeValuef(TH_HANDLE_VERTEX_SIZE) + 1.0f) * U.pixelsize);
+	immUniform1f("size", (1.4f * UI_GetThemeValuef(TH_HANDLE_VERTEX_SIZE)) * U.pixelsize);
 	immUniform1f("outlineWidth", 1.0f * U.pixelsize);
 
 	draw_fcurve_selected_handle_vertices(fcu, v2d, false, sel_handle_only, pos);