Compilation fix for Visual C++ .NET 2003 (msvc71)

Explanations:
/Zc:wchar_t is recognized by msvc71, /Zc:wchar_t- is not (the - is important and was introduced only with msvc >= msvc80)
Thus /Zc:wchar_t- is recognized as /Zc:wchar_t and this is not what we want :)
Default behavior of msvc71 is already /Zc:wchar_t-

Solution:
Test the msvc version and add the compiler flag only if compiler >= msvc80 (e.g MSVC_VERSION >= 1400)
Same for /D_CRT_SECURE_NO_DEPRECATE and /D_CRT_NONSTDC_NO_DEPRECATE, there were introduced with msvc >= msvc80

git-svn-id: svn://anonsvn.kde.org/home/kde/trunk/kdesupport/taglib@978720 283d02a7-25f6-0310-bc7c-ecb5cbfe19da