bc: lexer debugging, added some failing test cases

bc: lexer debugging, added some failing test cases

function                                             old     new   delta
bc_parse_push_block_flag                               -      47     +47
zbc_parse_body                                       107     121     +14
zbc_num_divmod                                       156     150      -6
zbc_lex_number                                       200     192      -8
zbc_parse_endBody                                    264     254     -10
bc_parse_startBody                                    47       -     -47
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 1/3 up/down: 61/-71)            Total: -10 bytes
   text	   data	    bss	    dec	    hex	filename
 982596	    485	   7296	 990377	  f1ca9	busybox_old
 982586	    485	   7296	 990367	  f1c9f	busybox_unstripped

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