bc: Add ptest.

Add ptest for OSS 'bc' by using 'bc' in the system to do calculation jobs according to the .b files from the source file.

Test example as below:
......
.00673400673400673400
“PASS: bc/div.b”
99836408603283573660347145562829683495827909199408566065153345558783\
9427595471.89114392327665123852
“PASS: bc/exp.b”
length(b)= 1406
“PASS: bc/fact.b”
......

If bc runs the .b files and does not crash, it would 'PASS', otherwise 'FAIL'.

Tested in qemux86-64, with kvm enabled, test cost 12 secs, so it should be a fast test.

Thanks to Ross Burton and Alexander Kanavin for the professional guidance.

Signed-off-by: Yan Xinkuan <yanxk.fnst@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>