db: don't store recursive struct members

db: don't store recursive struct members

Recently, (I think it may because I have improved get_other_name()) then
the DB has grown from 20GB to 42GB.  We are storing too much recursive
information like:

	foo->parent->parent->parent->parent->value = 2-400

This change looks for struct members with the same name and says we don't
store them.  So foo->parent->value gets stored, but
foo->parent->parent->value does not.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>