fix warnings about unused variables & parameters

Change-Id: Ia5816671267ea21dae0d90560b239c4498f9156c
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

qmake/generators/integrity/gbuild.cpp

@@ -417,6 +417,7 @@ QString GBuildMakefileGenerator::writeOne(QString filename, QString pathtoremove
 bool
 GBuildMakefileGenerator::openOutput(QFile &file, const QString &build) const
 {
+    Q_UNUSED(build)
     debug_msg(1, "file is %s", file.fileName().toLatin1().constData());
     QFileInfo fi(file);
     if (fi.filePath().isEmpty())

qmake/generators/mac/pbuilder_pbx.cpp

@@ -1797,6 +1797,7 @@ ProjectBuilderMakefileGenerator::reftypeForFile(const QString &where)
 
 QString ProjectBuilderMakefileGenerator::sourceTreeForFile(const QString &where)
 {
+    Q_UNUSED(where)
     // We always use absolute paths, instead of maintaining the SRCROOT
     // build variable and making files relative to that.
     return QLatin1String("<absolute>");

qmake/option.cpp

@@ -531,12 +531,11 @@ Option::fixString(QString string, uchar flags)
         string = QDir::cleanPath(string);
     }
 
-    bool localSep = (flags & Option::FixPathToLocalSeparators) != 0;
-    bool targetSep = (flags & Option::FixPathToTargetSeparators) != 0;
-    bool normalSep = (flags & Option::FixPathToNormalSeparators) != 0;
-
     // either none or only one active flag
-    Q_ASSERT(localSep + targetSep + normalSep <= 1);
+    Q_ASSERT(((flags & Option::FixPathToLocalSeparators) != 0) +
+             ((flags & Option::FixPathToTargetSeparators) != 0) +
+             ((flags & Option::FixPathToNormalSeparators) != 0) <= 1);
+
     //fix separators
     if (flags & Option::FixPathToNormalSeparators) {
         string = string.replace('\\', '/');

src/corelib/io/qsettings.cpp

@@ -890,7 +890,9 @@ StNormal:
                 ++j;
             }
 
-#ifndef QT_NO_TEXTCODEC
+#ifdef QT_NO_TEXTCODEC
+            Q_UNUSED(codec)
+#else
             if (codec) {
                 stringResult += codec->toUnicode(str.constData() + i, j - i);
             } else