Added special case for pid 0 when determining username on Windows.
Added special case for pid 0 when determining username on Windows.

AlanZatarain/psutil,marmolu/psutil,PFZheng/psutil,huson2012/psutil,tigerneil/psutil,Alwnikrotikz/psutil,zhengzheng/psutil,stupidcache/psutil,nmani1905/psutil,kiranvizru/psutil,huson2012/psutil,creativewild/psutil,shiva21/psutil,kiranvizru/psutil,skyshe/psutil,anfedorov/psutil,peter-hst/psutil,google-code-export/psutil,end18/psutil,chjwang/psutil,zhengzheng/psutil,jucapj/psutil,tigerneil/psutil,stupidcache/psutil,marmolu/psutil,creativewild/psutil,google-code-export/psutil,stupidcache/psutil,peter-hst/psutil,google-code-export/psutil,end18/psutil,anfedorov/psutil,djhaskin987/psutil,kiranvizru/psutil,skyshe/psutil,vmolsa/psutil,AlanZatarain/psutil,vmolsa/psutil,djhaskin987/psutil,tigerneil/psutil,shiva21/psutil,skyshe/psutil,PFZheng/psutil,chjwang/psutil,kiranvizru/psutil,vmolsa/psutil,nmani1905/psutil,end18/psutil,huson2012/psutil,tigerneil/psutil,djhaskin987/psutil,skyshe/psutil,vmolsa/psutil,end18/psutil,creativewild/psutil,jucapj/psutil,djhaskin987/psutil,Alwnikrotikz/psutil,google-code-export/psutil