bc: do not check for errors when parsing/running internal library

bc: do not check for errors when parsing/running internal library

function                                             old     new   delta
bc_lib_name                                            4       -      -4
bc_vm_run                                           1921    1900     -21
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(add/remove: 0/1 grow/shrink: 0/1 up/down: 0/-25)             Total: -25 bytes

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