add WSMAN_BUF_CAPACITY SDL unittest

[JumpingYang001]

I just add 1 SDL unittest here at first. Don't know how to verify omitest.log in unittest now, will add it once know it.
Test:

NitsTestWithSetup(TestBigString, TestWsbufSetup)
{
    String result;

    if(!TEST_ASSERT (MI_RESULT_OK == WSBuf_Init(&s_buf, 10)))
        NitsReturn;

    {
        result += TEST_STR_ENCODED;
        std::string str = string(10000 * 1024, '.');
        char *cstr = new char[str.length() + 1];
        strcpy(cstr, str.c_str());
        TEST_ASSERT (MI_RESULT_FAILED == WSBuf_AddString(&s_buf, cstr) );
        delete [] cstr;
    }

    TEST_ASSERT (MI_RESULT_OK == WSBuf_Destroy(&s_buf));
}
NitsEndTest

Get in /home/jumping/bld-omi/omi/Unix/output/var/log/omitest.log:
2019/01/10 04:54:40 [18801,18801] ERROR: wsbuf.c(531): EventId=20151 Priority=ERROR Wsman malloc exceeds reasonable limit: 10241032

[JumpingYang001]

Travis failed because SDL code have not check in yeah. :)