getNumLiveAttributes() is not right

TProgram::getNumLiveAttributes() is implemented as return getNumPipeInputs();
This is not correct, because gl_InstanceID for example is not an attribute.
Also compute shader inputs are not attributes.

Locate TProgram::getNumLiveAttributes() and trace how getNumPipeInputs() is used to derive the current count. Check the handling of gl_InstanceID and compute shader inputs, then verify that the resulting count includes only live attributes and add or run the relevant compiler tests if available.

Written by the indexing model from the issue text.