Fix small issue with c-src tests
Fix small issue with c-src tests

Main test Makefile expects "c_src" but for convenience I also
allow "c-src" and use that one as the prefix for the tests.

ninenines/erlang.mk,crownedgrouse/erlang.mk,ingwinlu/erlang.mk,jj1bdx/erlang.mk,rabbitmq/erlang.mk,nevar/erlang.mk,hairyhum/erlang.mk