arb_texture_buffer_range: Fix buffer alignment in ranges-2 test
The ranges-2 test was failing due to glTexBufferRange returning GL_INVALID_VALUE when the offset parameter wasn't GL_TEXTURE_BUFFER_OFFSET_ALIGNMENT byte aligned.
From the OpenGL 4.6 Core spec:
An INVALID_VALUE error is generated if offset is not an integer multiple of the value of TEXTURE_BUFFER_OFFSET_ALIGNMENT.
Edited by Anthony Pesch