ENH: Made RunSingleCommand take a double as its timeout length.

Source/cmSystemTools.cxx

@@ -420,7 +420,7 @@ bool cmSystemTools::RunSingleCommand(
   int *retVal, 
   const char* dir,
   bool verbose,
-  int timeout)
+  double timeout)
 {
   if(s_DisableRunCommandOutput)
     {

Source/cmSystemTools.h

@@ -191,7 +191,7 @@ public:
    * function will return false.
    */
   static bool RunSingleCommand(const char* command, std::string* output = 0,
-    int* retVal = 0, const char* dir = 0, bool verbose = true, int timeout = 0);
+    int* retVal = 0, const char* dir = 0, bool verbose = true, double timeout = 0.0);
 
   /**
    * Parse arguments out of a single string command