[win32] fix some unit tests

[Montellese]

These commits fix the unit test setup and some unit tests on win32.

• The first commit fixes building and running unit tests from Visual Studio.
• The second commit silences a warning due to an unused variable (only used by non-win32 platforms)
• The third commit fixes CXBMCTestUtils::ReferenceFilePath() which is used in a lot of places to get a valid path to a test file. It probably worked on non-win32 platforms but was broken on win32 due to putting together paths ending with \ and starting with /.
• The last commit excludes TestRarFile from the unit test project for now because compilation fails due to 47f3d83 and I don't really know what the proper fix is. On win32 the missing S_IFLNK is never used in any core code only in the unit tests.

[Memphiz]

Looks good for me - for the testrarfile either just define the missing S_IFLINK for the windows part in the cpp or revert the offender.

[Montellese]

OK I have changed the last commit to define S_IFLNK if it isn't already defined.

[Montellese]

I started some manual jenkins builds with unit tests enabled:

• OSX-64: http://jenkins.kodi.tv/job/OSX-64/2324/
• Linux-64: http://jenkins.kodi.tv/job/LINUX-64/2096/
• Android-ARM (doesn't run unit tests): http://jenkins.kodi.tv/job/Android-ARM/2241/
• Win32 didn't work or at least it didn't get past the checkout in 34 minutes: http://jenkins.kodi.tv/job/WIN-32/2375/

When I run unit tests locally on win32 I still get a few failures but this fixes some of them and doesn't break other platforms.

[Memphiz]

Fyi - Unit Tests are not hooked up for win32 jenkins