Resubmit with inconsistent override warnings fixed.

Removing dynamic indexing of vectors and matrices will require copying
the indexed nodes in case they are written. Any type of l-value node that
doesn't have side effects may need to be copied. Add a copying function
for all typed node classes so that this copying can be performed.

Private copy constructors are used to implement the deepCopy function in
order to make maintenance easier. With copy constructors, each subclass
only needs to take care of copying its own members, and not the base
class members, which reduces the possibility of errors. Copy constructors
are disabled for all node classes that don't support deep copying by
inheriting TIntermNode from angle::NonCopyable.

Assignment operator is disabled for all node classes through inheriting
angle::NonCopyable. This applies also to classes that now get the private
copy constructor.

Explicit copy constructor and assignment operator declarations are added
to some classes which show up in node member variables to make code
clearer.

BUG=angleproject:1116
TEST=angle_unittests

Change-Id: I7964976f5dac7dfd745b8c6612ca06fb01d271c4
Reviewed-on: https://chromium-review.googlesource.com/295080Tested-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>