o change the mapping arrays to have a zero offset rather than base 1;
this eliminates lots of signo adjustments and brings the code
back inline with the original netbsd code
o purge use of SVR4_SIGTBLZ; SVR4_NSIG is the only definition for
how big a mapping array is
o change the mapping loops to explicitly ignore signal 0
o purge some bogus code from bsd_to_svr4_sigset
o adjust svr4_sysentvec to deal with the mapping table change
Enticed into fixing by: Coverity Prevent analysis tool
Glanced at by: marcel, jhb
