Replaced all other autoconf-defined platform macros (HAVE_LINUX and
HAVE_MACOSX, WIN32 already done) with those ones defined by compiler.
Not yet remove the definitions from autoconf, in case someone will use
the old macros anyways. Remove in future.
get rid of direct GLUT dependency
+ mac_gl_common.m: fixed copyright + relicense (as the only author)
+ destroy_gl_context - noop for empty (zeroed, not initialized) context
+ GL: attach the context (will be useful later when running at the same
time Syphon and GL display)
Do not abort if compile/link fails but return 0. Some of callers already
expect returning 0 on error.
+ print the errors with ERROR severity to be more obvious in program output
Some macros are quite common so it is perhaps more wise to use a
separate header.
Also moved ref_count_init_once and ref_count_terminate last to misc.h.
Call glutInit for macOS. This is rather a workaround to fix a problem
when running 'uv --capabilities' with RTDXT and Syphon. Initialization
of GLUT in Syphon then fails because glutInit is skipped since NSApp is
a non-NULL (from initialization of GL context). Further GLUT call then
fail.
