Support aliases for simplify, deriv and etc.

[sys27]

Support aliases for simplify, deriv and etc. (for function which is not calculated in parser)

[sys27]

Restrict the direct return/pass of expressions, return/pass a lambda instead. For example:

simplify(x * x) -> simplify((x) => x * x)

So, if the function accepts the "raw" expression (instead of the result of the calculation), then we need to specify it explicitly. And simplify(x * x) will be executed as:

• calculate x * x, for example, 10 is assigned to x, then x * x -> 100
• execute simplify(x * x) as simplify(100)

It will fix the issue but at the same time will increase the complexity of xFunc grammar/expression.

Related: #628.