Implement C side hook lists in parallel with the existing Scheme hook

[David Hampton]

Log Message:
-----------
Implement C side hook lists in parallel with the existing Scheme
hook lists.  Allows hooks to be easily installed from either
Scheme or C code.

Tags:
----
gnucash-gnome2-dev

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/app-file:
        gnc-file.c
    gnucash/src/app-utils:
        prefs.scm
    gnucash/src/core-utils:
        Makefile.am
        gw-core-utils-spec.scm
    gnucash/src/gnome:
        dialog-new-user.c
        top-level.c
    gnucash/src/gnome-utils:
        gnc-menu-extensions.scm
    gnucash/src/report/report-gnome:
        report-gnome.scm
    gnucash/src/scm:
        main.scm

Added Files:
-----------
    gnucash/src/core-utils:
        gnc-hooks.c
        gnc-hooks.h