This commit fixes two bugs, the first when recording
on Windows where the user is unable to stop the capture cleanly
and one regarding the VCD output being malformed due to null characters in strings.
Reading from the stdin buffer is generally better behaved on both platforms,
while not as performant. The user can now cancel the capture by terminating the source
program or issuing a keyboard interrupt.
The issue with string capture having trailing null characters is fixed,
which in the best case confuses GTKwave, or in the worst case segfaults it.
