COMP: fix some warnings

Source/kwsys/SystemTools.cxx

@@ -1405,7 +1405,7 @@ unsigned long SystemTools::FileLength(const char* filename)
     }
   else
     {
-      return fs.st_size;
+      return static_cast<unsigned long>(fs.st_size);
     }
 }
 
@@ -2310,7 +2310,7 @@ SystemTools::GetFilenameWithoutLastExtension(const kwsys_stl::string& filename)
 
 bool SystemTools::FileHasSignature(const char *filename,
                                    const char *signature, 
-                                   unsigned long offset)
+                                   long offset)
 {
   if (!filename || !signature)
     {

Source/kwsys/SystemTools.hxx.in

@@ -268,7 +268,7 @@ public:
   static kwsys_stl::string GetCurrentWorkingDirectory();
 
   ///! return true if the file has a given signature (first set of bytes)
-  static bool FileHasSignature(const char* filename, const char *signature, unsigned long offset = 0);
+  static bool FileHasSignature(const char* filename, const char *signature, long offset = 0);
 
   /**
   *  Try to locate the file 'filename' in the directory 'dir'.