1) Using XMgr or ACE/gr as plotting tool

   In order to use XMgr or ACE/gr as plotting tool it has to be told to read
   any data from STDIN. This can be achieved defining PLOTTOOL in FuncCalc's
   Makefile as follows:

        -DPLOTTOOL='"xmgr -source stdin 1>/dev/null 2>&1"'

   In order to perform autoscaling of both axis on read as well define:

        -DPLOTTOOL='"xmgr -autoscale xy -source stdin 1>/dev/null 2>&1"'


2) Using flex instead of lex

   Currently, the lexer input files *.l do not support flex, since they use
   lex-specific input redirection, which flex does not allow.
