compile swift with OpenSSL on Mac
Merge pull request #48 from LipuFei/fix-mac-multispec

compile swift with OpenSSL on Mac.
Merged for the moment.. but need some re-work. It should be a separate config for Tribler specific builds
fix #52: segfault while downloading many files at the same time
check StorageFiles if they are operational in Storage::ParseSepc()
add print_backtrace() for Windows
fix memory allocation and releasing in constructors and destructors
print_backtrace() only for debug version