bc: rename lexer variables, use smallints where appropriate

bc: rename lexer variables, use smallints where appropriate

function                                             old     new   delta
bc_parse_expr_empty_ok                              1966    1972      +6
zdc_parse_expr                                       514     518      +4
zbc_lex_number                                       177     174      -3
dc_num_printChar                                      24      21      -3
bc_lex_whitespace                                     41      38      -3
bc_lex_name                                           69      66      -3
bc_lex_lineComment                                    36      33      -3
bc_lex_assign                                         31      28      -3
zbc_parse_name                                       472     468      -4
zbc_vm_process                                       836     831      -5
zdc_program_execStr                                  512     506      -6
zbc_parse_text_init                                   59      53      -6
bc_num_printNewline                                   51      45      -6
bc_num_printHex                                       67      61      -6
bc_num_printDigits                                   137     131      -6
zbc_program_assign                                   426     419      -7
zbc_parse_stmt_possibly_auto                        1682    1675      -7
zbc_program_exec                                    3977    3964     -13
zbc_program_print                                    683     656     -27
zbc_lex_next                                        2233    2161     -72
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/18 up/down: 10/-183)         Total: -173 bytes

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