Initialize OpenSSL locking functions
Remove _GLIBCXX_CONCEPT_CHECKS debug define

This debug feature does not support any C++11 features.
It breaks for example the compilation of vector<unique_ptr>.

The upstream issue is:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57011
Merge pull request #653 from BtbN/opensslthreads

Initialize OpenSSL locking functions