Autoconf, Fix AM_CONFIG_HEADER, AM_PROG_CC_STDC and INCLUDES

Since automake 1.13, the AM_CONFIG_HEADER is obsolete and will fail unless is
it replaced with AC_CONFIG_HEADERS.
minor, fixed a warning about rememberlevel param
minor copyright update.
fixed a bug which makes the administration menu missing

When gcompris --reread-menu was run, one time on 2
the administration menu was added, the other time it
was removed.