QtCore/IO: Fix some warnings on Windows (64bit).

- Warnings about conversion from size_t to int
- Unused variable.

Change-Id: I4a79fa6dc4b95551a64d282ae4307b0edff41201
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qfilesystemengine_win.cpp

@@ -589,8 +589,6 @@ QString QFileSystemEngine::owner(const QFileSystemEntry &entry, QAbstractFileEng
 bool QFileSystemEngine::fillPermissions(const QFileSystemEntry &entry, QFileSystemMetaData &data,
                                         QFileSystemMetaData::MetaDataFlags what)
 {
-    QAbstractFileEngine::FileFlags ret = 0;
-
 #if !defined(QT_NO_LIBRARY)
     if((qt_ntfs_permission_lookup > 0) && (QSysInfo::WindowsVersion & QSysInfo::WV_NT_based)) {
         resolveLibs();

src/corelib/io/qiodevice_p.h

@@ -167,7 +167,7 @@ private:
         size_t newCapacity = qMax(capacity, size_t(QIODEVICE_BUFFERSIZE));
         while (newCapacity < required)
             newCapacity *= 2;
-        int moveOffset = (where == freeSpaceAtEnd) ? 0 : newCapacity - len;
+        const size_t moveOffset = (where == freeSpaceAtEnd) ? 0 : newCapacity - size_t(len);
         if (newCapacity > capacity) {
             // allocate more space
             char* newBuf = new char[newCapacity];

src/corelib/io/qprocess_win.cpp

@@ -282,7 +282,7 @@ QProcessEnvironment QProcessEnvironment::systemEnvironment()
     // This is not the case the other way round.
     if (wchar_t *envStrings = GetEnvironmentStringsW()) {
         for (const wchar_t *entry = envStrings; *entry; ) {
-            int entryLen = wcslen(entry);
+            const int entryLen = int(wcslen(entry));
             if (const wchar_t *equal = wcschr(entry, L'=')) {
                 int nameLen = equal - entry;
                 QString name = QString::fromWCharArray(entry, nameLen);