Remove some type field accessor macros

Remove some type field accessor macros

This removes TYPE_FIELD_PRIVATE, TYPE_FIELD_PROTECTED,
TYPE_FIELD_IGNORE, and TYPE_FIELD_VIRTUAL.

In c-varobj.c, match_accessibility can be removed entirely now.  Note
that the comment before this function was incorrect.

Acked-By: Simon Marchi <simon.marchi@efficios.com>
Reviewed-by: Keith Seitz <keiths@redhat.com>