Directory polish.

- Parsing/lexing a simple language of mathematical expressions.

- Perform a simple treatment on abstract syntax trees; namely translating
  some function expressions into simple algebraic counterparts (see module
  Transl).

To compile it:

. ./compile_fcn

To clean it:

. ./clean

To run it:

./fcn -s "1 + 2"
./fcn -s "sqrt (1) + 2"
