Add MaxInt tests to gl-uniform-arrays.html

Add tests to gl-uniform-arrays.html that ensure there is no overflow when calling
getUniformLocation with an array uniform that has an index greater than or equal
to MaxInt.

For instance, 'gl.getUniformLocation(program, "myuniform[4294967296]")' should
fail.
MaxInt is confusing, because the maximum integer that JS can safely handle is 2^53.

So probably named it MaxInt32?  the value should be 2^32-1 = 4294967295.