C: -DF displays now also the symbolname for each SV/AV/HV/* in the c file
C 1.42_51: preserve TAINT -T and -t, fixes #148 and #151

-T/-t requires perlcc -T/-t option, but the state is now properly restored in
the executable also.
Fixes issue #151 (all tests pass now for perlcc -T -r t/CORE/comp/opsubs.t)

Make B::C taint safer
As sideeffect this also fixes #148, bareword filehandles.