Build protobuf v2.6.1 from source zip, VS2019
- Create x64 Platform
- Set Output Directory of non-gtest projects to $(Configuration)\
- Define _SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS in the 3 lib projects and
  protoc and tests.
- Insert spaces before uses of the macros ETC and PATH_SEPARATOR in the files:
  - command_line_interface_unittest.cc
  - parser_unittest.cc
- Set Debug Information Format to /Z7

- 4 tests fail (more fail when run inside VS2019; need to run in separate
  cmd.exe)
  - None are critical to the operation of protobuf (especially in memory), so
    let's say it's okay to ignore.

[  FAILED  ] 4 tests, listed below:
[  FAILED  ] CommandLineInterfaceTest.CwdRelativeInputShadowedError
[  FAILED  ] CommandLineInterfaceTest.MsvsFormatErrors
[  FAILED  ] DiskSourceTreeTest.DiskFileToVirtualFile
[  FAILED  ] DiskSourceTreeTest.VirtualFileToDiskFile

- Build Debug and Release
- Run extract_includes.bat
- Copy include/, protoc.exe, and libproto*.lib to destinations