COMP: Avoid incompatible pointer warning
COMP: Avoid incompatible pointer warning

In SharedForward, the call to execvp warned on MinGW because the
signature declared in process.h has an extra const.  We use an explicit
cast to convert the pointer type.

johnkit/vtk-dev,berendkleinhaneveld/VTK,jeffbaumes/jeffbaumes-vtk,hendradarwin/VTK,jeffbaumes/jeffbaumes-vtk,mspark93/VTK,keithroe/vtkoptix,msmolens/VTK,Wuteyan/VTK,candy7393/VTK,aashish24/VTK-old,demarle/VTK,candy7393/VTK,jeffbaumes/jeffbaumes-vtk,mspark93/VTK,johnkit/vtk-dev,daviddoria/PointGraphsPhase1,hendradarwin/VTK,collects/VTK,biddisco/VTK,daviddoria/PointGraphsPhase1,hendradarwin/VTK,arnaudgelas/VTK,ashray/VTK-EVM,hendradarwin/VTK,mspark93/VTK,msmolens/VTK,aashish24/VTK-old,demarle/VTK,daviddoria/PointGraphsPhase1,daviddoria/PointGraphsPhase1,demarle/VTK,Wuteyan/VTK,gram526/VTK,candy7393/VTK,collects/VTK,berendkleinhaneveld/VTK,ashray/VTK-EVM,candy7393/VTK,spthaolt/VTK,daviddoria/PointGraphsPhase1,sumedhasingla/VTK,biddisco/VTK,naucoin/VTKSlicerWidgets,sankhesh/VTK,sankhesh/VTK,msmolens/VTK,candy7393/VTK,naucoin/VTKSlicerWidgets,cjh1/VTK,berendkleinhaneveld/VTK,demarle/VTK,daviddoria/PointGraphsPhase1,sankhesh/VTK,cjh1/VTK,jmerkow/VTK,SimVascular/VTK,ashray/VTK-EVM,msmolens/VTK,mspark93/VTK,biddisco/VTK,jmerkow/VTK,SimVascular/VTK,sumedhasingla/VTK,Wuteyan/VTK,johnkit/vtk-dev,keithroe/vtkoptix,SimVascular/VTK,sumedhasingla/VTK,biddisco/VTK,demarle/VTK,jmerkow/VTK,msmolens/VTK,biddisco/VTK,sankhesh/VTK,sumedhasingla/VTK,johnkit/vtk-dev,Wuteyan/VTK,naucoin/VTKSlicerWidgets,arnaudgelas/VTK,arnaudgelas/VTK,keithroe/vtkoptix,Wuteyan/VTK,keithroe/vtkoptix,sumedhasingla/VTK,jeffbaumes/jeffbaumes-vtk,msmolens/VTK,demarle/VTK,johnkit/vtk-dev,candy7393/VTK,ashray/VTK-EVM,collects/VTK,msmolens/VTK,aashish24/VTK-old,biddisco/VTK,demarle/VTK,cjh1/VTK,jeffbaumes/jeffbaumes-vtk,arnaudgelas/VTK,naucoin/VTKSlicerWidgets,aashish24/VTK-old,sankhesh/VTK,gram526/VTK,mspark93/VTK,spthaolt/VTK,hendradarwin/VTK,sankhesh/VTK,sankhesh/VTK,ashray/VTK-EVM,gram526/VTK,naucoin/VTKSlicerWidgets,spthaolt/VTK,johnkit/vtk-dev,ashray/VTK-EVM,gram526/VTK,hendradarwin/VTK,johnkit/vtk-dev,biddisco/VTK,ashray/VTK-EVM,naucoin/VTKSlicerWidgets,mspark93/VTK,SimVascular/VTK,jmerkow/VTK,berendkleinhaneveld/VTK,spthaolt/VTK,msmolens/VTK,keithroe/vtkoptix,Wuteyan/VTK,berendkleinhaneveld/VTK,jeffbaumes/jeffbaumes-vtk,candy7393/VTK,spthaolt/VTK,keithroe/vtkoptix,keithroe/vtkoptix,SimVascular/VTK,collects/VTK,sankhesh/VTK,jmerkow/VTK,mspark93/VTK,arnaudgelas/VTK,berendkleinhaneveld/VTK,sumedhasingla/VTK,SimVascular/VTK,cjh1/VTK,demarle/VTK,berendkleinhaneveld/VTK,keithroe/vtkoptix,arnaudgelas/VTK,sumedhasingla/VTK,gram526/VTK,spthaolt/VTK,jmerkow/VTK,aashish24/VTK-old,jmerkow/VTK,sumedhasingla/VTK,gram526/VTK,collects/VTK,hendradarwin/VTK,Wuteyan/VTK,SimVascular/VTK,ashray/VTK-EVM,SimVascular/VTK,cjh1/VTK,cjh1/VTK,jmerkow/VTK,spthaolt/VTK,collects/VTK,aashish24/VTK-old,gram526/VTK,candy7393/VTK,mspark93/VTK,gram526/VTK