Fix some warnings from -Wundef

Other warnings come from kwsys, so the flag can't be enabled.

Source/cmCommandArgumentParser.cxx

@@ -279,7 +279,7 @@ typedef short int yytype_int16;
 #define YYSIZE_MAXIMUM ((YYSIZE_T) -1)
 
 #ifndef YY_
-# if YYENABLE_NLS
+# if defined YYENABLE_NLS && YYENABLE_NLS
 #  if ENABLE_NLS
 #   include <libintl.h> /* INFRINGES ON USER NAME SPACE */
 #   define YY_(msgid) dgettext ("bison-runtime", msgid)
@@ -701,7 +701,7 @@ while (YYID (0))
    we won't break user code: when these are the locations we know.  */
 
 #ifndef YY_LOCATION_PRINT
-# if YYLTYPE_IS_TRIVIAL
+# if defined YYLTYPE_IS_TRIVIAL && YYLTYPE_IS_TRIVIAL
 #  define YY_LOCATION_PRINT(File, Loc)                  \
      fprintf (File, "%d.%d-%d.%d",                      \
               (Loc).first_line, (Loc).first_column,     \

Source/cmake.cxx

@@ -953,7 +953,7 @@ int cmake::AddCMakePaths()
   cMakeSelf = cmSystemTools::GetRealPath(cMakeSelf.c_str());
   cMakeSelf += "/cmake";
   cMakeSelf += cmSystemTools::GetExecutableExtension();
-#if __APPLE__
+#ifdef __APPLE__
   // on the apple this might be the gui bundle
   if(!cmSystemTools::FileExists(cMakeSelf.c_str()))
     {