Fix dumping vertex attributes
Fix dumping vertex attributes

When AttribDesc::AttribDesc fills in the data fields, it tries to find
number of columns from size and type only. This works OK for uniforms
(and presumably feedback transform attributes), because they can have
type like GL_FLOAT_VEC3, but this fails for vertex attributes, where
types can only be scalar (those acceptable to glVertexAttribPointer).

This patch special-cases filling in the data fields for vertex
attributes, which then lets qapitrace show the correct structure of
vertex buffers.

apitrace/apitrace,apitrace/apitrace,apitrace/apitrace,apitrace/apitrace