Prevent a crash of example/FFT_test.cir.
Buffer 'buf' in function drawlingrid() has been too small.
Increase 'buf' size, and add some protection.
The example file examples/plot/test-small-plot.cir
shows the limits of plotting:
difference in two numbers at digit 14 is plotted well.
at digit 15 is plotted with bugs.
at digit 16 is reduced to integer.
consider compiling with
-O1 -D_FORTIFY_SOURCE=2
for gcc, and
/GS
for visual studio.
Holger Vogt