OpenCL C spec editorial fixes (#532)

* adjust column widths for vector numeric indices table

* address space updates

* add attributes for OpenCL C features
reflow the table for address space behavior

* unify gentype syntax

* add feature dictionary

* Apply suggestions from code review

Co-authored-by: Anastasia Stulova <38433336+AnastasiaStulova@users.noreply.github.com>

Co-authored-by: Anastasia Stulova <38433336+AnastasiaStulova@users.noreply.github.com>

Author: bashbaug