* give an error when declaring a class as conforming to a forward-declared
    interface: the compiler does not/cannot check whether the class
    implements all required methods in that case, and it moreover leads to
    crashes (mantis #24184). Older versions of Delphi did allow this (and
    don't check whether the interface methods are implemented either), but
    that's simply a (similar) bug in Delphi that has been fixed in XE at
    least
  * fixed compilation of webtbs/tw2727 after this fix

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@24177 3ad0048d-3df7-0310-abae-a5850022a9f2