[ENHANCEMENT] Change format of %{ %}

[Arthur Schwarz]

All the code placement options end in '}' except "%{" which ends with "$}". For 
conformity maybe its time to obsolete the "%}" ending and change to '}'

This then becomes:
%{ } obsoleting %{ %}
%code { }
%code top { }
%code required { }
%code provided { }

thanks
art