add wolfCrypt error codes IO_FAILED_E "Input/output failure" and SYSLIB_FAILED_E "System/library call failed";
tests/api.c and tests/unit.c: flush stdout for error message in Fail() macro, add fflush(stdout) after printf()s, print success message at end of unit_test(), and send several error messages to stderr instead of stdout;
wolfcrypt/test/test.c: add fallthrough macro definition of printf() that pairs it with fflush(stdout);
unit.h: in definition of macro AssertPtr(), add PRAGMA_GCC("GCC diagnostic ignored \"-Wpedantic\"");
sp_int.c: refactor several lingering instances of "if (0) { ... }" code pattern to #if 0 ... #endif.