Modified easylogging++.h

Changed this:

#if defined(__APPLE__)
#if TARGET_OS_MAC
#define _MAC 1
#endif //TARGET_OS_MAC
#endif //defined(__APPLE__)

To this:

#if defined(__APPLE__)
#define _MAC 1
#endif //defined(__APPLE__)

This makes it possible to #include easylogging++.h before other headers, without getting compilation errors on a Mac.
P.S. sorry about the indentation, Xcode copy and paste auto-indents the code.