of the "embedded" server

Problem: mysqltest_embedded failed to load ha_innodb_plugin library
on some platforms (due to some unresolved references).

Fix: on FreeBSD use -export-dynamic flag building mysqltest_embedded.
That allows to use its global symbols to resolve references in the
dynamically loaded plugin library.


libmysqld/examples/Makefile.am:
  Fix for bug #50667: The InnoDB plugin prevents initialization
  of the "embedded" server
    - use -export-dynamic (on FreeBSD/DragonFly) building
  mysqltest_embedded to allow using its global symbols 
  to resolve references in the dynamically loaded plugin libraries.