c_example.x: add error message on dlopen() failure
c_example.x: add error message on dlopen() failure

Add human readable error message in case of failure to load shared
library.

Signed-off-by: Andrey Gelman <01507057b38b758911b62352314fe43a9c5992c8@datarcs.com>
Signed-off-by: Andrey Gelman <01507057b38b758911b62352314fe43a9c5992c8@gmail.com>

opcm/pcm,opcm/pcm,opcm/pcm,opcm/pcm