problems with integration

[parisse]

Numeric constants and numeric constant functions are less confusing: g:=x+1, g(3) could be the constant function x+1 evaluated at 3, value x+1, or the function x->x+1 evaluated at 3, value 4 (current returned value with a warning). If g:=1, there is nothing to replace, g(3) is less confusing, hence no warning. 1(x) is parsed as 1*x with a warning since nobody would enter 1 as 1(x).
Implicit multiplication is *not* supported by the CAS parser, a few shortcuts are supported like 2x, 2x^3, 2sin(x), and some syntaxic sugar (with warning) happens for expressions like (x+1)(x+2) where * is guessed from context since x can not be a function and a variable in the same time.
With the fix, ((x->x)+x)(3) will return like ((y->y)+x)(3), i.e. x(3)+3, with a warning.