1GENERAL: erract - variable for error handling

"erract" is a variable for error handling. If an error occurs within a
macro the value of "erract" is executed as command. By default the "exit"
command is executed, i.e. the program returns to interactive input.

Example: set erract="show\; quit"
         (With this setting of erract, in case of an error, a listing
         of all global variables is given, and the program is stopped.)