fix preprocessor error for __linux__ is defined to empty.
fix qtss_maxprintf redefined

When USE_DEFAULT_STD_LIB is not defined and __USE_MAX_PRINTF__ is
defined, we have two qtss_maxprintf implementation in
SafeStdLib/InternalStdLib.cpp.
Android has no sys/sysctl.h
Android defines __in_port_t instead of in_port_t
Android has no signal.h but sys/signal.h
Android has no libcrypt, use MD5 instead.
Build DarwinStreamServer on Android