What steps will reproduce the problem?
1. Checkout r87 on Windows.
2. Build mozc_tool.exe with Qt and Visual Studio.
3. Run mozc_tool.exe.

What is the expected output? What do you see instead?
mozc_tool.exe should run without any error.
mozc_tool.exe crashes with RtlValidateHeap failure actually.

Please use labels and text to provide additional information.
Some Qt functions such as QSting::toStdString on which Mozc currently depends 
assume that both mozc_tool.exe and Qt DLLs are using the same Visual C++ 
runtime libraries.
mozc_tool.exe as of r87 violates this rule as follows:
- Qt DLLs (e.g. QtCore4.dll) are using dynamically-linked version of Visual C++ 
runtime.
- mozc_tool.exe (as of r87) is using statically-linked version of Visual C++ 
runtime.
The attached patch fixes this mismatch.