Fix some MSVC conversion warnings

Change-Id: Ib2c1fdb7b84f89201136438362ab5962126ec929
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/corelib/io/qprocess_win.cpp

@@ -452,7 +452,7 @@ static QByteArray qt_create_environment(const QProcessEnvironmentPrivate::Map &e
                 copy.insert(rootKey, QString::fromLocal8Bit(systemRoot));
         }
 
-        int pos = 0;
+        qsizetype pos = 0;
         auto it = copy.constBegin();
         const auto end = copy.constEnd();
 
@@ -460,7 +460,7 @@ static QByteArray qt_create_environment(const QProcessEnvironmentPrivate::Map &e
         static const wchar_t nul = L'\0';
 
         for ( ; it != end; ++it) {
-            uint tmpSize = sizeof(wchar_t) * (it.key().length() + it.value().length() + 2);
+            qsizetype tmpSize = sizeof(wchar_t) * (it.key().length() + it.value().length() + 2);
             // ignore empty strings
             if (tmpSize == sizeof(wchar_t) * 2)
                 continue;

src/corelib/text/qbytearray.cpp

@@ -647,7 +647,7 @@ QByteArray qUncompress(const uchar* data, qsizetype nbytes)
         return invalidCompressedData();
 
     forever {
-        ulong alloc = len;
+        const auto alloc = len;
         int res = ::uncompress((uchar*)d.data(), reinterpret_cast<uLongf*>(&len),
                                data+4, nbytes-4);
 

src/corelib/text/qstringconverter.cpp

@@ -1790,7 +1790,7 @@ std::optional<QStringConverter::Encoding> QStringConverter::encodingForHtml(cons
     if (pos != -1) {
         pos = header.indexOf("charset=", pos);
         if (pos != -1) {
-            pos += qstrlen("charset=");
+            pos += int(qstrlen("charset="));
             if (pos < header.size() && (header.at(pos) == '\"' || header.at(pos) == '\''))
                 ++pos;