bc: do not perform domr limit checks when they can't work (e.g. on 32-bit arches)

bc: do not perform domr limit checks when they can't work (e.g. on 32-bit arches)

Also, optimize printing of messages with fixed limit strings
by including limits as strings.

function                                             old     new   delta
bc_num_ulong                                         103      95      -8
bc_lex_number                                        296     281     -15
dc_lex_token                                         701     684     -17
bc_lex_name                                           90      73     -17
bc_num_shift                                          72      54     -18
bc_lex_token                                        1299    1280     -19
bc_parse_stmt                                       1868    1768    -100
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/7 up/down: 0/-194)           Total: -194 bytes
   text	   data	    bss	    dec	    hex	filename
 985814	    485	   7296	 993595	  f293b	busybox_old
 985526	    485	   7296	 993307	  f281b	busybox_unstripped

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