Fix for Mantis #21015 .

symdef.pas:
  * tobjectdef.find_implemented_interface: use equal_defs to ensure that equal specializations of interfaces are found as well
  * getparaencoding: use globals.CP_NONE instead of just CP_NONE, because defcmp contains a cp_none enum as well.

+ added test

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@25609 3ad0048d-3df7-0310-abae-a5850022a9f2