Fix a couple of compiler warnings (#62)

I see a few compiler warnings on gcc 9.2:

src/ghdl.cc: In function ‘Yosys::RTLIL::SigSpec get_src(std::vector<Yosys::RTLIL::Wire*>&, GhdlSynth::Net)’:
src/ghdl.cc:123:43: warning: ‘valzx’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  123 |           switch(((val01 >> i)&1)+((valzx >> i)&1)*2)
      |                                    ~~~~~~~^~~~~
src/ghdl.cc:123:26: warning: ‘val01’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  123 |           switch(((val01 >> i)&1)+((valzx >> i)&1)*2)
      |                   ~~~~~~~^~~~~
src/ghdl.cc:99:26: warning: ‘val’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   99 |           bits[i] = (val >> i) & 1 ? RTLIL::State::S1 : RTLIL::State::S0;
      |                     ~~~~~^~~~~

These both appear to be spurious, but initialize them to 0 to avoid the
warning.

0 files changed, 0 insertions, 0 deletions