the methods IsFile() and GetFilePath() to BDiskDevice, and
BDiskDeviceRoster::GetFileDeviceForPath().
* Added new syscalls to implement this functionality.
* Added new flag B_DISK_DEVICE_IS_FILE.
* Fixed wrong operator precedence assumption in the BDiskDevice class at
several places.
* Minor cleanup.
git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@28052 a95241bf-73f2-0310-859d-f6bbb57e9c96