bc: fix handling of comment/string interactions while buffering input

function                                             old     new   delta
zbc_lex_next                                        1965    1982     +17
zbc_num_divmod                                       150     156      +6
bc_read_line                                         411     394     -17
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(add/remove: 0/0 grow/shrink: 2/1 up/down: 23/-17)              Total: 6 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed