[README] Example 01

This example implements a simple calculator. It reads expressions of
the form "Int op=+|-|*|/ Int" from stdin. 
An empty line as well as the input "<ctrl>c" stops the process.

Use the shell script 'mx' to create the executable. 
Don't forget 
1) to check the setting of the environment variable STYXDIR in 'mx'
2) to add $STYXDIR/lib to your library path.

Execute the program by 'calctut'.