src: Fix possible heap-use-after free for OpenSSL global locking

This is simply programming error, but it is interesting that using
libstdc++ does not reveal this error.  With clang++-libc++, we got
std::system_error: mutex lock faild: Invalid argument.  This is
because we did not give a name to lock object, so it is immediately
destructed.  I think this will fix the reported crash on Mac OSX.
tiny-nghttpd: Simplify timer event handling