Fix 'Dead nested assignment' from scan-build-10

This is the warning:

In file included from print_test.c:47:
./../print.c:203:9: warning: Although the value stored to 'neg' is used in the enclosing expression, the value is never actually read from 'neg'
                dot = neg = space = plus = left = zero = alt = h = l = q = z = 0;
                      ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.