configure.ac: do not use deprecated macros - AC_HELP_STRING AC_ERROR

Replace with AS_HELP_STRING and AC_MSG_ERROR respectively, as spotted by
autoupdate.

Note that the suggested AC_CANONICAL_SYSTEM > AC_CANONICAL_TARGET change
is not addressed here since that requires very extensive testing.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
1 file changed