[giac] fix for Limit[cos(x),∞]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25371 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
[giac] SolveODE: add y'= if first argument not an equation eg SolveODE[y / x, y, x] is the same as SolveODE[y'=y / x, y, x]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25372 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e