Merge pull request #838 from dfaure-kdab/Wundef

Add missing `defined`, detected by -Werror=undef

tinyxml2.cpp

@@ -103,7 +103,7 @@ distribution.
 #if defined(_WIN64)
 	#define TIXML_FSEEK _fseeki64
 	#define TIXML_FTELL _ftelli64
-#elif defined(__APPLE__) || (__FreeBSD__)
+#elif defined(__APPLE__) || defined(__FreeBSD__)
 	#define TIXML_FSEEK fseeko
 	#define TIXML_FTELL ftello
 #elif defined(__unix__) && defined(__x86_64__)