vchoi_fork

[svn-r13945] Description:
    Modify semantics for constant messages slightly, to allow them to be
deleted, but not modified.  This works around the issue where "old" style
groups are being created with the symbol table message marked constant in
the 1.6 (and prior) branch, but the 1.8 branch needs to remove the symbol table
message when the group has been changed to the "new" style (upon insertion
of a link that the "old" style can't handle).

Tested on:
    Mac OS X/32 10.4.10 (amazon)
    Linux/32 2.6 (chicago)
    Linux/64 2.6 (chicago2)