define FI_MSG_PREFIX

Signed-off-by: Reese Faucette <rfaucett@cisco.com>
Merge pull request #182 from rfaucett/prefix

define FI_MSG_PREFIX
Fix dlopen configure switch. This just does not seem to work when specified as a enable option. Reverted back to with option.
Merge pull request #183 from pmmccorm/master

Fix dlopen configure switch.
Based on my reading of the autoconf manual, AC_ARG_WITH is to be used with external packages, so I believe that this change is desired anyway, versus using AC_ARG_ENABLE.