Version: 5.2.1

Changes:

    * Move unsupported STL headers to stlport/deprecated folder
    * Do not include ctime in stlport_prefix.h
    * Inlude __Named_exception imple. in stlport static library 
    * Fix warnings under MSVC and GCC, and most of them are issues of unused parameters
    * Use sgx_read_rand for generating rand numbers
    * Replace unique(...) in _algo.h with LLVM imple.
    * Add no storage (zero-length) bitset in _bitset.h
    * Disable features rely on I/O operations
    * Disable wchar support
    * Define _NOTHREADS, _STLP_NO_THREADS, _STLP_USE_NEWALLOC, _STLP_NO_EXTENSIONS by default
    * Use SGX C++ runtime library instead
    * Disable unsupported data types and interfaces in _cstdio.h, _cstdlib.h, _ctime.h, _cwchar.h, etc.
    * Add using _STLP_VENDOR_EXCEPT_STD::bad_alloc
    * Let _STLP_THROW_BAD_ALLOC call _STLP_ABORT() directly, do not use puts() and exit(1)
    * Do not use puts() in _STLP_THROW_MSG()
    * Use SGX spinlock instead
    * Add _sgx.h for SGX configurations
    * Do not include Windows/Linux system headers directly
