Patch for: T28462

Hi,

In RAS_2DFilterManager.cpp::RenderFilters() if a depth or luminance texture is required the active texture unit gets changed from (GL_TEXTURE)0 to 1 or 2 and doesn't get reverted back. At minimum this causes the wrong texture matrix to be set to identity leading to problems when texunit 0 is used to convey texturecoords.