Resolve warnings about unused variables.

Source/cmGlobalVisualStudio6Generator.cxx

@@ -200,7 +200,6 @@ void cmGlobalVisualStudio6Generator
       tt != orderedProjectTargets.end(); ++tt)
     {
     cmTarget* target = *tt;
-    cmMakefile* mf = target->GetMakefile();
     // Write the project into the DSW file
     const char* expath = target->GetProperty("EXTERNAL_MSPROJECT");
     if(expath)

Source/cmLocalVisualStudioGenerator.cxx

@@ -84,7 +84,6 @@ cmLocalVisualStudioGenerator
                   const char* newline_text)
 {
   bool useLocal = this->CustomCommandUseLocal();
-  const cmCustomCommandLines& commandLines = cc.GetCommandLines();
   const char* workingDirectory = cc.GetWorkingDirectory();
   cmCustomCommandGenerator ccg(cc, configName, this->Makefile);
   RelativeRoot relativeRoot = workingDirectory? NONE : START_OUTPUT;

Source/cmNinjaNormalTargetGenerator.cxx

@@ -564,6 +564,7 @@ void cmNinjaNormalTargetGenerator::WriteLinkStatement()
     // for instance ARG_MAX is 2096152 on Ubuntu or 262144 on Mac
     commandLineLengthLimit = ((int)sysconf(_SC_ARG_MAX))-linkRuleLength-1000;
 #else
+    (void)linkRuleLength;
     commandLineLengthLimit = -1;
 #endif
   }

Source/cmVisualStudio10TargetGenerator.cxx

@@ -907,7 +907,6 @@ bool cmVisualStudio10TargetGenerator::OutputSourceSpecificFlags(
   cmSourceFile* source)
 {
   cmSourceFile& sf = *source;
-  cmLocalVisualStudio7Generator* lg = this->LocalGenerator;
 
   std::string objectName;
   if(this->GeneratorTarget->ExplicitObjectName.find(&sf)