Bytecode 1.16: use our own walksymtable

also use Bytecode,-s > 5.18.
honor TEST_VERBOSE=2 for bytecode also (plctest)

use bwarn for Bytecode warnings.
most plctest cases seem to work now.
Bytecode: skip empty xcv_start (e.g. with 5.18 main_cv)

apparently with 5.18 main_cv->START can now be empty.

also add a flushing "\n" to the src files.
simplify -H/-s logic in t/bytecode.t
use proper -Iblib/arch -Iblib/lib, not -Mblib
C: revise sharedlibrary ptr to 0x40_0000

re-enable TODO for t/issue130.t BC test > 5.18thr
fix t/testc.sh 309 result