bugfix OpenGL performance hog

ofShader is rolling its own manual location table for attributes.

The position attribute, which is the first attribute, was set to 1, leaving attribute 0 unset. This did lead to catastrophic performance losses on certain graphics cards (ATI, OS X).

See also: "In OpenGL you MUST enable Attrib 0"

in: <http://www.chromium.org/nativeclient/how-tos/3d-tips-and-best-practices>
Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>