CELIX-119: Updated resolver and related files to remove APR.

git-svn-id: https://svn.apache.org/repos/asf/incubator/celix/trunk@1600110 13f79535-47bb-0310-9956-ffa450edef68
CELIX-119: Added source file for pthread abstraction.

git-svn-id: https://svn.apache.org/repos/asf/incubator/celix/trunk@1600111 13f79535-47bb-0310-9956-ffa450edef68