Don't output newline instead if label in initial DFA state.

Don't output newline instead if label in initial DFA state.

Rationale: the equivalence of initial label to
're2c::label_counter_t::FIRST' is NOT a proper criterion
and pretty-printing shouldn't rely on it. The real criterion
is something like "(first re2c block OR any use block in '-r'
mode) AND first condition in'-c' mode", but it's spurious and
introduces unnecessary complications.

Droping this newline allows us drop equivalence operator for
labels.

Used the following bash script to ensure that all the changes
in tests are caused by missing newline(s):

    #!/bin/bash

    for f2 in *.temp
    do
        f1=${f2%.temp}

        diff1=`diff $f1 $f2 | grep '^< ' | wc -l`
        diff1_line=`diff $f1 $f2 | grep '^< #line' | wc -l`
        diff1_newline=`diff $f1 $f2 | grep '^< $' | wc -l`
        diff2=`diff $f1 $f2 | grep '^> ' | wc -l`
        diff2_line=`diff $f1 $f2 | grep '^> #line' | wc -l`

        # missing: only newlines and line directives
        if [[ $diff1 -ne $((diff1_line + diff1_newline)) ]]
        then
            echo "FAIL1: $f1"
            exit 1
        fi

        # added: only line directives
        if [[ $diff2 -ne $diff2_line ]]
        then
            echo "FAIL2: $f1"
            exit 1
        fi

        # the number of missing line directives
        # equals to the number of added line directives
        if [[ $diff1_line -ne $diff2_line ]]
        then
            echo "FAIL4: $f1"
            exit 1
        fi
    done

    echo "OK"