Force QT_NO_ICONV on win32:!win32-msvc*

This behaviour was changed in Ide9800f6 to suppress
macro redefinition warnings for MSVC, but MinGW
has iconv support and therefore configure does not
set QT_NO_ICONV, which prevents compilation on win32-g++
as QIconvCodec does not support Windows.

Change-Id: Ic3c4ccceb3eaf9542c95b0c27847ca5ab51849b7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>

src/corelib/codecs/codecs.pri

@@ -54,7 +54,7 @@ contains(QT_CONFIG,icu) {
                     SOURCES += codecs/qiconvcodec.cpp
                     DEFINES += GNU_LIBICONV
             }
-    } else:!win32 {
+    } else:!win32-msvc* {
         DEFINES += QT_NO_ICONV
     }
     win32 {