Note that this is left undefined by the spec, but glGetBoolean converts
non-zero integers to GL_TRUE, so this makes things symmetric.

Bug swiftshader:90

Change-Id: Ie2d3b2b8d66e63f542f758ddc6482b451fb4140d
Reviewed-on: https://swiftshader-review.googlesource.com/c/21511Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>