ESSL 3.00 spec section 3.4 mentions that the second operand in a logical
&& or || preprocessor operation is evaluated only if the first operand
doesn't short-circuit the expression. The non-evaluated part of a
preprocessor expression may also have undefined identifiers.

Make the expression parser follow the spec by ignoring errors that are
generated inside short-circuited expressions. This includes undefined
identifiers and divide by zero.

BUG=angleproject:347
TEST=dEQP-GLES3.functional.shaders.preprocessor.undefined_identifiers.*
     angle_unittests

Change-Id: Ieed02a71298af838f784a5d1197d4f4a9ba0e3c8
Reviewed-on: https://chromium-review.googlesource.com/295033Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Tested-by: Olli Etuaho <oetuaho@nvidia.com>