* added (limited) GetLastOSError by emulation of Win32 and *nix behaviour in the RTL

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28947 3ad0048d-3df7-0310-abae-a5850022a9f2
  * minor optimization (don't clear the result of GetDynLibsErrorStr twice)

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@28948 3ad0048d-3df7-0310-abae-a5850022a9f2