Customwizard: Add a simple preprocessor.

Allowing for nesting sections depending on Javascript expression using
the (expanded) wizard field variables as in:

-- test.pro.template:
QT = core
@if "%NETWORK_CHECKBOX%" == "true"
QT += network
@endif
Rubber-stamped-by: Alessandro Portale <alessandro.portale@nokia.com>

src/plugins/projectexplorer/customwizard/customwizardparameters.cpp

@@ -28,6 +28,7 @@
 **************************************************************************/
 
 #include "customwizardparameters.h"
+#include "customwizardpreprocessor.h"
 
 #include <coreplugin/mimedatabase.h>
 #include <coreplugin/icore.h>
@@ -644,5 +645,24 @@ void CustomWizardContext::reset()
                             mdb->preferredSuffixByType(QLatin1String(CppTools::Constants::CPP_HEADER_MIMETYPE)));
 }
 
+QString CustomWizardContext::processFile(const FieldReplacementMap &fm, QString in)
+{
+
+    if (in.isEmpty())
+        return in;
+
+    if (!fm.isEmpty())
+        replaceFields(fm, &in);
+
+    QString out;
+    QString errorMessage;
+    if (!customWizardPreprocess(in, &out, &errorMessage)) {
+        qWarning("Error preprocessing custom widget file: %s\nFile:\n%s",
+                 qPrintable(errorMessage), qPrintable(in));
+        return QString();
+    }
+    return out;
+}
+
 } // namespace Internal
 } // namespace ProjectExplorer