[fpc-pascal] Feature Request: Evalution Box instead of Calculator

[Bill Yau]

        Although I would like to transfer my programming from TP to
FPC, I found that I cannot test some source lines directly without
writing a full program. I suggest to implement the evalutation box in
TP7 to the IDE, enabling users to input a full expression and evaluate
the result, and support more operator/system functions(binary op,
sincos, ...). I hope it can replace the calculator now in the IDE
completly.
       If that is possible, I think the evaluation box should also
allow the user to calculate with some user-defined functions in the
source code to help them check the correctness of the function without
extra coding.