* handle_ln_const: if/else branches were swapped, correct values are: ln(0)=-Inf and ln(-#)=NaN.
* handle_ln_const and handle_sqrt_const handle all arguments, not just invalid ones, so calling code can be simplified.

git-svn-id: http://svn.freepascal.org/svn/fpc/trunk@27837 3ad0048d-3df7-0310-abae-a5850022a9f2