Better support for MacOS and arm64

[DavJCosby]

cyCore.h wont compile for arm64 architectures due to these lines:

#if !defined(CY_NO_INTRIN_H) && !defined(CY_NO_EMMINTRIN_H) && !defined(CY_NO_IMMINTRIN_H)
# include <immintrin.h>
#endif

Unless I've got things set up wrong on my end, it seems that the deprecated gluErrorString() function is unavailable on MacOS as well. Because of that, this section from cyGL.h won't compile:

while ( (error = glGetError()) != GL_NO_ERROR) {
	*outStream << "OpenGL ERROR: " << sourcefile << " (line " << line << "): ";
	if ( call ) *outStream << call << " triggered ";
	*outStream << gluErrorString(error) << std::endl;
}

This PR adds && !defined(__aarch64__) to that first chain of definition checks, instructing the compiler to skip including these intel intrinsics on at least some incompatible platforms. Further, it reimplements gluErrorString() via conditional compilation for Apple devices.