Fix path detection with --std= parameter

Fixes path detection when compilers have been told to follow a standard, e.g. with -DCMAKE_CXX_FLAGS=--std=c++98.
To see the passed defines, try this with and without the --std parameter:
gcc -E -dM --std=c99 - < /dev/null | grep linux

src/porting.cpp

@@ -369,7 +369,7 @@ void initializePaths()
 	/*
 		Linux
 	*/
-	#elif defined(linux)
+	#elif defined(linux) || defined(__linux)
 
 	char buf[BUFSIZ];
 	memset(buf, 0, BUFSIZ);
@@ -465,7 +465,7 @@ void initializePaths()
 	/*
 		Linux
 	*/
-	#elif defined(linux)
+	#elif defined(linux) || defined(__linux)
 
 	// Get path to executable
 	std::string bindir = "";