Check at ./configure time that the kernel was built with kallsyms
support. If the kernel doesn't have CONFIG_KALLSYMS defined the
modules will still compile cleanly but will not be loadable. So
we really want to catch this early during ./configure. Note that
we do not require CONFIG_KALLSYMS_ALL but it may be safely defined.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#6