In this initial commit the Path class contains two methods for
converting path separators. I want to move cppcheck path handling
to direction that we internally have paths with / separator. And
convert from/to native separators when needed.
This commit adds setfile() method to FileLocation class. The setfile
method converts in Windows path separators to internally used Unix
separators. And getfile() converts path separators back to Windows
separators. This fixes bugs that error reports had mixed path
separators in paths.
