front: Add VerticalSync to config file to silence glide warnings.

Rice also uses this setting, but since we hadn't been defining it, it
has always fallen back to its defined default value (0). Glide does not
define a default value, however, so it throws errors in the logcat. I'm
pretty sure that the glide has been using a de facto value of zero all
this time.  So this commit shouldn't change any behavior other than
silence a logcat message.