STYLE: Fix typos

Source/cmCacheManager.cxx

@@ -334,7 +334,7 @@ bool cmCacheManager::SaveCache(const char* path)
     cmSystemTools::ReportLastSystemError("");
     return false;
     }
-  // before writting the cache, update the version numbers
+  // before writing the cache, update the version numbers
   // to the 
   char temp[1024];
   sprintf(temp, "%d", cmMakefile::GetMinorVersion());

Source/cmFileCommand.cxx

@@ -119,7 +119,7 @@ bool cmFileCommand::HandleWriteCommand(std::vector<std::string> const& args,
     {
     std::string error = "Internal CMake error when trying to open file: ";
     error += fileName.c_str();
-    error += " for writting.";
+    error += " for writing.";
     this->SetError(error.c_str());
     return false;
     }

Source/cmWriteFileCommand.cxx

@@ -75,7 +75,7 @@ bool cmWriteFileCommand::InitialPass(std::vector<std::string> const& args)
     {
     std::string error = "Internal CMake error when trying to open file: ";
     error += fileName.c_str();
-    error += " for writting.";
+    error += " for writing.";
     this->SetError(error.c_str());
     return false;
     }