Update used MinGW-builds toolchain

Change-Id: I2bfbb25605471e4496de25ff27b00ad254449b08
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Akseli Salovaara <akseli.salovaara@digia.com>

doc/src/platforms/supported-platforms.qdoc

 /****************************************************************************
 **
-** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Copyright (C) 2014 Digia Plc and/or its subsidiary(-ies).
 ** Contact: http://www.qt-project.org/legal
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -105,7 +105,7 @@
     \row    \li Microsoft Windows 7 (32-bit)
                                      \li MSVC 2010 SP1
     \row    \li Microsoft Windows 7 (32-bit)
-                                     \li \l{http://sourceforge.net/projects/mingwbuilds/files/host-windows/releases/4.8.0/32-bit/threads-posix/dwarf/x32-4.8.0-release-posix-dwarf-rev1.7z}{MinGW-builds gcc 4.8.0 (32-bit)}
+                                     \li \l{http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/4.9.1/threads-posix/dwarf/i686-4.9.1-release-posix-dwarf-rt_v3-rev2.7z/download}{MinGW-builds gcc 4.9.1 (32-bit)}
     \row    \li Microsoft Windows 8 (32-bit and 64-bit)
                                      \li MSVC 2012 SP2
     \row    \li Microsoft Windows 8.1 (32-bit and 64-bit)

doc/src/platforms/windows.qdoc

@@ -325,8 +325,8 @@
             \endlist
         \li Windows SDK 7.
         \li A MinGW toolchain with g++ version 4.7 or higher. Qt 5 is tested regularly with a \
-            \l{http://sourceforge.net/projects/mingwbuilds/files/host-windows/releases/4.8.0/32-bit/threads-posix/dwarf/x32-4.8.0-release-posix-dwarf-rev1.7z}
-            {32 bit gcc 4.8.0 toolchain} from the \l{http://mingwbuilds.sourceforge.net}{MinGW-builds}
+            \l{http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/4.9.1/threads-posix/dwarf/i686-4.9.1-release-posix-dwarf-rt_v3-rev2.7z/download}
+            {32 bit gcc 4.9.1 toolchain} from the \l{http://mingw-w64.sourceforge.net/}{MinGW-w64}
             project.
 
     \endlist