Added more info to ES3 only errors in parser

Added the same info as Angle's for ES3 only errors.

Change-Id: I2f11b34b06f8e1cc1b0a200d568c709ca35469ab
Reviewed-on: https://swiftshader-review.googlesource.com/3639
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>