Installer Fix on some Windows 7 64-bit Systems

One some Windows machines the command processor is not invoked properly when
running the WScript.Run method. The same PostgreSQL 9.0.1-1 one click installer
that worked perfrectly fine on one Windows 7 64-bit machine did not work as
expected on another machine with same OS. Adding the command processor
explicity: 

"%comspec% /c " &

to the first parameter on all objShell.Run calls in the installer WScript files
below resolves this issue!

For installruntimes.vbs file used the following mod:
iRet = objShell.Run("%comspec% /c " & """" & strPackage & """ /q:a /c:""msiexec
/i vcredist.msi /qb!""", 0, True)

For initcluster.vbs, loadmodules.vbs and startupcfg.vbs used the following mod:
DoCmd = objShell.Run("%comspec% /c " & objTempFolder.Path & "\" & strBatchFile,
0, True)