Change all occurances of QofAccessFunc function pointers to QofParam, so

[Linas Vepstas]

Log Message:
-----------
Change all occurances of QofAccessFunc function pointers
to QofParam, so that the access func can be passed a type.
Time like these, I wish the C programming language had 'lambda'.

Modified Files:
--------------
    gnucash/src/engine:
        qofclass.h
        qofquery.c
        qofquerycore-p.h
        qofquerycore.c
        qofquerycore.h