intel: Move validation of context version into intelInitContext

intel: Move validation of context version into intelInitContext

Each driver (i830, i915, i965) used independent but similar code to
validate the requested context version. With the rececnt arrival of GLES3,
that logic has needed an update. Rather than apply identical updates to
each drivers validation code, let's just move the validation into the
shared routine intelInitContext.

This refactor required some incidental changes to functions
i830CreateContext and intelInitContext. For each function, this patch:
    - Adds context version parameters to the signature.
    - Adds a DRI_CTX_ERROR out param to the signature.
    - Sets the DRI_CTX_ERROR at each early return.

Tested against gen6 with piglit egl-create-context-verify-gl-flavor.
Verified that this patch does not change the set of exposed EGL context
flavors.

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>