Add _daylight _timezone and _tzname

Add an alias without underscore
Move the definition to the common header

git-svn-id: https://mingw-w64.svn.sourceforge.net/svnroot/mingw-w64/trunk@5821 4407c894-4637-0410-b4f5-ada5f102cad1
Move asprintf/vasprintf inlines away from extern C++ blocks

git-svn-id: https://mingw-w64.svn.sourceforge.net/svnroot/mingw-w64/trunk@5822 4407c894-4637-0410-b4f5-ada5f102cad1