glsl: Add new overload of program_resource_visitor::visit_field method

glsl: Add new overload of program_resource_visitor::visit_field method

The outer-most record is passed into the visit_field method for
the first field.  In other words, in the following structure:

    struct S1 {
        vec4 v;
        float f;
    };

    struct S {
        S1 s1;
        S1 s2;
    };

    uniform Ubo {
        S s;
    };

s.s1.v would get record_type = S (because s1.v is the first non-record
field in S), and s.s2.v would get record_type = S1.  s.s1.f and s.s2.f
would get record_type = NULL becuase they aren't the first field of
anything.

This new overload isn't used yet, but the next patch will add several
uses.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
Cc: "9.2 9.1" mesa-stable@lists.freedesktop.org