Explicitly instantiate TIntermTraverser::traverse(TIntermNode *).

Explicitly instantiate TIntermTraverser::traverse(TIntermNode *).

(on behalf of RewriteAtomicFunctionExpressions)
The compile will occasionally choose to inline all instances of this
function, and therefore not export this entrypoint into the object file,
leaving other TUs (RewriteAtomicFunctionExpressions) with missing
link symbols.

Bug: angleproject:3752
Change-Id: Ida778bcd897a85567680911a88aae88a3797aa93
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1721954
Commit-Queue: Jeff Gilbert <jgilbert@mozilla.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Gbp-Pq: Topic porting-s390x
Gbp-Pq: Name Explicitly-instantiate-TIntermTraverser-traverse-TIntermN.patch