Fix bootstrap script to cope with changed AC_INIT arguments.

Fix bootstrap script to cope with changed AC_INIT arguments.

* bootstrap: When extracting PACKAGE and VERSION from AC_INIT
arguments, be sure to remove a 'GNU ' prefix and lowercase the
package name for PACKAGE.  Also set PACKAGE_NAME and PACKAGE_URL
appropriately for GNU software.  Pass these variables to the
make commands creating tests/package.m4 and other files.
* Makefile.am (edit): Fix substitution of PACKAGE_NAME and
PACKAGE_STRING.
* libltdl/config/announce-gen.m4sh: Use @PACKAGE@ not
@PACKAGE_STRING@.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>