function setAttributePrefix(prefix) {
    defaults.attribPrefix = prefix;
  }
Sets the default attrib prefix

When writing shaders I prefer to name attributes with `a_`, uniforms with `u_` and varyings with `v_`
as it makes it clear where they came from. But, when building geometry I prefer using unprefixed names.

In otherwords I'll create arrays of geometry like this

    var arrays = {
      position: ...
      normal: ...
      texcoord: ...
    };

But need those mapped to attributes and my attributes start with `a_`.

@deprecated see {@link module:twgl.setDefaults}
@param {string} prefix prefix for attribs
@memberOf module:twgl/attributes