tools: fix install source path for openssl headers

This part is broken for a very long time. We noticed the problem while
using jxcore native interface with embedded openssl. I've also sent a
pull request to node.js repo. The problem may affect a native addon
using builtin openssl. `opensslconf.h` is overwritten with
`deps/openssl/conf/opensslconf.h`

PR-URL: https://github.com/iojs/io.js/pull/1354


Reviewed-By: Shigeki Ohtsu <ohtsu@iij.ad.jp>