Overriding PACKAGE_TARNAME?

[Warren Young]

I maintain a package called MySQL++, which uses autoconf.  In previous 
versions of the library, we used AM_INIT_AUTOMAKE, calling the package 
'mysql++'.  For the upcoming version of the library, we have switched 
over to the newer AC_INIT syntax.

But now, 'make dist' is creating tarballs called mysql---x.y.z.tar.gz 
instead of mysql++-x.y.z.tar.gz.  I can see why this is happening in the 
configure file, but I don't like it.

How do we either prevent AC_INIT from turning + signs into - signs when 
creating the PACKAGE_TARNAME macro, or override PACKAGE_TARNAME once 
it's been defined?