Fix various build warnings when using Visual Studio

While verifying a defect I had to build the windows thrift C++ library and found a number of compiler warnings that needed to be cleaned up. As part of cleaning these up, I found that additional compilers were also posting warnings.

Acceptance Criteria:

1. I can build successfully with Visual Studio 2010 targeting x86 debug mode with /WX (warnings are errors).
2. I can build successfully with Visual Studio 2010 targeting x86 release mode with /WX (warnings are errors).
3. I can build successfully with Visual Studio 2010 targeting x64 debug mode with /WX (warnings are errors).
4. I can build successfully with Visual Studio 2010 targeting x64 release mode with /WX (warnings are errors).
5. I can build successfully with Visual Studio 2015 targeting x86 debug mode with /WX (warnings are errors).
6. I can build successfully with Visual Studio 2015 targeting x86 release mode with /WX (warnings are errors).
7. I can build successfully with Visual Studio 2015 targeting x64 debug mode with /WX (warnings are errors).
8. I can build successfully with Visual Studio 2015 targeting x64 release mode with /WX (warnings are errors).

Follow-up: I got pretty close to this ideal goal, but not quite there. There were improvements nonetheless and I was able to successfully build with Visual Studio 2010, 2012, 2013, and 2015, Debug or Release, Win32 or x64 modes and pass unit tests. As such I didn't meet all the criteria of removing every warning, but the majority are gone.