Register a path provider for Qt instead of using PathService::Override

Change-Id: I465a5465ec4189b077a8c1cbab7485c628eca899
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Use arm_neon_optional from armv7 onward if not explicitly enabled

This makes our behavior consistent with chromium if the
Qt toolchain does not explicitly enable NEON instructions,
which would result in undefined symbols otherwise.

Change-Id: Idc4f355714ede4206f4650664f6c24784100e7d8
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>