Generalize 'kernels' and 'tower'.


git-svn-id: https://fricas.svn.sourceforge.net/svnroot/fricas/trunk@1561 b0c55286-4f34-0410-a049-a1e7e93b0762
Better handling of algebraic integrals.


git-svn-id: https://fricas.svn.sourceforge.net/svnroot/fricas/trunk@1562 b0c55286-4f34-0410-a049-a1e7e93b0762
Change formula for derivatives of asec, asech, acsc and acsch.


git-svn-id: https://fricas.svn.sourceforge.net/svnroot/fricas/trunk@1563 b0c55286-4f34-0410-a049-a1e7e93b0762