The variables "[fReopenDebugLog](https://github.com/bitcoin/bitcoin/blob/fa24439ff3d8ab5b9efaf66ef4dae6713b88cb35/src/util.h#L53)" and "[fRequestShutdown](https://github.com/bitcoin/bitcoin/blob/fae78fa81802b5387054715c339f286ef436408e/src/init.cpp#L128)" should [use the data type "sig_atomic_t"](https://www.securecoding.cert.org/confluence/display/c/SIG31-C.+Do+not+access+shared+objects+in+signal+handlers) (instead of "bool").

I reported this issue for [another evolving software](https://github.com/Electric-Coin-Company/zcash/issues/678) before.

{
    return fwrite(str.data(), 1, str.size(), fp);
}
static void DebugPrintInit()
{
    assert(mutexDebugLog == NULL);
    mutexDebugLog = new boost::mutex();
    vMsgsBeforeOpenLog = new list<string>;
}
void OpenDebugLog()
{
    boost::call_once(&DebugPrintInit, debugPrintInitFlag);
    boost::mutex::scoped_lock scoped_lock(*mutexDebugLog);
    assert(fileout == NULL);
    assert(vMsgsBeforeOpenLog);
    boost::filesystem::path pathDebug = GetDataDir() / "debug.log";
    fileout = fopen(pathDebug.string().c_str(), "a");
    if (fileout) setbuf(fileout, NULL); 
    
    while (!vMsgsBeforeOpenLog->empty()) {
        FileWriteStr(vMsgsBeforeOpenLog->front(), fileout);
        vMsgsBeforeOpenLog->pop_front();
    }
    delete vMsgsBeforeOpenLog;
    vMsgsBeforeOpenLog = NULL;
}
bool LogAcceptCategory(const char* category)