* do not warn when internally generated if nodes are simplified

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@29292 3ad0048d-3df7-0310-abae-a5850022a9f2
* set nf_internal for if nodes generated by assert, prevent warning for assert(true); resolves #26467

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@29293 3ad0048d-3df7-0310-abae-a5850022a9f2