gl_x11: always require some GLX API functions, avoid dlsym()

The functions glXGetProcAddressARB() and glXQueryExtensionsString() were
loaded using dlsym(). This could fail when compiling to libmpv, because
then dlopen(NULL, ...) will look in the main program's list of
libraries, and the libGL linked to libmpv is never considered. (Don't
know if this somehow could be worked around.) The result is that using
vo_opengl with libmpv can fail.

Avoid this by not using dlsym(). glXGetProcAddressARB() was already used
directly in the same file, and that never caused any problems. (Still
add it to the configure test.) glXQueryExtensionsString() is documented
as added in GLX 1.1 - that's ancient.
gl_x11: remove workaround for PPC OSX 10.4

Added in 2010 with commit 4a8486f8 (svn commit 30994). I doubt anyone
still uses X11 on OSX, and we probably don't support 10.4 either.
gl_wayland: remove probably unneeded workaround

This would imply eglGetProcAddress() doesn't work correctly, but using
dlsym() does. For now get rid of it - it won't work in libmpv, and we'll
probably need a better workaround if it's still broken.

This code was in the initial wayland commit.
gl_common: remove dlsym() fallback

See previous commits.
player: hide audio/video codec and file format messages

None of these are very important usually. For error analysis, the plain
log is useless anyway, and this information is still printed with "-v".